BLE System Integration for Fitness Devices: How to Connect Them to Your App

How to make fitness devices to "talk" to your mobile app? The short answer is through BLE integration. But, probably, you already know that. And in this guide, you’ll find out how to implement it into your app.

In two words, integrating BLE-based devices with your app means enabling wireless communication between your software and hardware devices. It can be smartwatches, heart rate monitors, or fitness equipment that transmit real-time data to the fitness app.

The demand for fitness apps remains strong, especially for those accompanied by smart devices. According to Statista, top fitness and workout apps reached 25.15 million global downloads in January 2025, showing a 7.8% increase from January 2024. But a fitness app retention rate remains a key issue after downloading. And BLE integration with mobile apps can help you solve this problem.

BLE-based devices are pivotal in fitness tracking app development due to their efficiency in power use and ease of pairing — they enable companies to provide their customers with convenient solutions for wellness app development that require very little maintenance and zero technical knowledge to pair up with users’ devices. BLE technology is also critical for e-scooter sharing app development, providing users with real-time data like battery status and trip information.

Let’s uncover some technical details of the BLE connection. GATT regulates the data transfer between two BLE-enabled devices. It stands for Generic Attribute Profile and defines two devices with an exclusive connection that communicate using the Services and Characteristics concepts.

Take a look at the following scheme, and we’ll explain it right after:

• GATT Server is divided into several services. For example, it can be a Blood Pressure Server that consists of several services.
• Services divide the data into blocks (Characteristics) that are logically needed to provide a specific service. For the Blood Pressure Server, the services are Blood Pressure Service and Device Information Service.
• Characteristics are containers with data points and certain values. The Blood Pressure Service displays such units as Intermediate Cuff Pressure, Blood Pressure Measurement, and Blood Pressure Feature. The Device Information Service shows Manufacturer Name String, Hardware Revision String, and Model Number String. A string is text information.
• Descriptors provide additional information about characteristics and their value.

Here’s a table that demonstrates the hierarchy of the GATT:

Another important part of BLE communication is the difference between central and peripheral devices. Central devices initiate the connection, while peripheral devices accept the responses.

A central BLE device can be connected to multiple peripheral devices at the same time. For peripheral devices, it’s the opposite. They can only be connected to one central device at a time. For example, a user’s phone (central device) can be connected to a fitness tracker, a heart rate ring, or smart dumbbells (peripherals) simultaneously, while each one of these devices can be connected to a single iOS or Android device.

However, these are only general rules. With a proper configuration, a device can act as a peripheral and a central device simultaneously, allowing it to connect to multiple central devices at once. The number of connections is technically unlimited, but in practice, there’s always a certain limit. It’s possible to reach up to 20 connections.

There are also such terms as GATT Client and GATT Server. They are often compared with central and peripheral roles, but these are different concepts. While central and peripheral roles define the connectivity structure, Client and Server refer to how data is managed and exchanged. In other words, Client devices request data, while Servers store and provide access to it.

BLE system integration can be extended with Mesh Bluetooth technology. It lets devices work together over long distances by sending messages to other devices. Bluetooth SIG documentation states that a device can still communicate with another device even if it is out of range of the central device. This is possible as long as other close devices can forward the message to the central device.

Mesh technology can be used in fitness apps that work with BLE-enabled devices, like heart rate sensors, smart scales, and exercise equipment. This way, you’ll make sure that your data is always in sync, that the transmission power is strong, and that you can analyze it on different devices.

These technical details can help you estimate the cost to build a Fitbit or similar fitness app, since these features can make the app more complex.

To give you a short break, watch what Todd Gilligan, Innovation Lead at Force USA, says about cooperation with Stormotion.

Another difference is that Bluetooth Classic has an active connection for a limited time (from a few seconds to several hours). BLE, on the other hand, has a continuous connection in sleep mode, which is the main reason for considerably reduced power consumption.

Now, let’s look at how BLE integrations can be used in the fitness industry.

Bluetooth Low Energy Use Cases in the Fitness Industry

All of us regularly use fitness bands and smartwatches. This is one of the most common BLE integration use cases. But the technologies, including when you develop a mental health app, go far beyond that and include numerous IoT devices. A BLE device acting as a bridge between the physical object and the digital world ensures seamless communication and data exchange.

Such integrations are often showcased at major health and fitness conferences, inspiring innovation across the industry.

Smart Mats

BLE-based smart mats for exercise and yoga analyze users' posture and exercise positions, offering recommendations on how to improve them. They also count the repetition of the exercise and keep a record of workouts.

Many companies sell these mats: YogiFi, SmartMat, Otari, and many others. The basic functionality is pretty much the same, but some providers offer additional gym app features that increase costs. Otari, for example, has a camera that uses AI to watch people while they exercise and gives them voice instructions.

If you want to learn more about building yoga applications, we have an article about it:

Smart Glasses & Traning for Olympics

Let’s take a look at one of the most interesting examples of IoT in the fitness industry. It’s a company called Solos that sells smart glasses. Riders often use Solos glasses to train for the Olympics.

These glasses use BLE technology and Augmented Reality to give athletes real-time data like speed, distance, cadence, calorie count, and heart rate. It can also connect with popular cycling apps like Strava, MapMyRide, and TrainingPeaks. Users can see the data on their glasses' screen thanks to an intuitive interface.

Such innovative devices show how IoT in wearable devices connects physical activity and digital health. You can find out more details in our wearable application development guide.

iBeacons & Bluetooth Devices for Gym Management Automation

BLE integration doesn’t necessarily have to be about providing fitness devices to your customers. It can also be used for management and marketing services. You can use iBeacons for such purposes.

Beacons are BLE devices that constantly send radio waves that other BLE- or Bluetooth-enabled devices can detect. Their main goal is to force the device they're communicating with to perform specific actions, such as opening a webpage or a mobile app.

When users' devices are in range, they do what the beacon asks, making them useful for business. But first, consider the pros and cons of ANT or Bluetooth to figure out the best protocol for your gym automation tasks.

Still, iBeacons depend on the location permission, which users rarely give. This can make the BLE integration strategy less effective.

Let’s take a look at several use cases of iBeacons:

All of that can be done even if you don’t have a fitness app. But if you do, you get more detailed customer information. You can personalize your campaigns and adjust your approach to clients’ needs.

What is a protocol? You can think about it as a language that the device “speaks” and that has to be used for communication. But the fact that devices are based on the same wireless network (in our case, using BLE) doesn’t mean they have the same protocol. In addition, each device on the network has a unique Media Access Control (MAC) address.

So, the challenge comes when we have several BLE-based elliptical machines that all have different protocols for integration and communication. In other words, they all receive commands and requests differently.

For example, one device doesn’t require anything for connection. You simply perform a BLE connection (enable the “Connect” button). Another protocol requires one line of code, and a third one might need three lines of code sent in a specific order with a setup delay.

The same thing works for communication itself. If we want to change the speed of elliptical machines from different providers, the prompt for that can be different for all of them. Some might specifically require a line that starts with the “3, 2 …” number and ends with “20”. This is how the device will understand that it needs to do something with the speed settings.

Following the general logic, all devices might have different line specifications for different commands. And every single detail from the order of numbers in the line to the line length is important. Even the slightest deviation from the protocol will give errors.

What’s even more exciting in integrating BLE into React Native is that developers often don’t know what protocols they’re dealing with. Just like in real life, when you approach a person, you can’t be sure what language they speak.

In such cases, we try to communicate with the device using various numbers and command combinations to figure out what the device uses. Surely, there are some “unspoken” rules of how protocols work.

When a BLE device returns responses to developers following certain protocol features, developers can figure out how the device is set up and easily talk to it. This allows them to create React Native fitness apps that work with various BLE devices.

Here’s the summary of the steps you should take to integrate multiple BLE devices that have different protocols.

1. Your fitness device provider and the protocol of the device can be whatever.
2. Your development team or Tech Partner tries to communicate with the device using different “languages”.
3. When they finally get an interpretable reply, they define the protocols’ structure.
4. Now, they know how to connect and communicate with the device in the right “language.”

Learn how to develop a personal trainer app that meets all your needs by following our recommendations and professional advice.

For fitness app developers involved in BLE development, there are minimal chances that their hardware provider doesn’t offer an SDK/APIs. If that happens, they can refer you to their tech partners who have solutions for their products.

So, you should follow these five steps when opting for a partnership with a third-party fitness device provider:

1. Think about what device(s) you’re looking for and start exploring the options.
2. Find a hardware provider who offers users a full-on, ready-to-use solution.
3. Check if the provider has an SDK/API. If yes, make sure they meet your business needs. For example, an API that establishes the connection between fitness equipment and an Android phone app is irrelevant to you if you’re building an iOS application. If they don’t, think about alternatives.
4. Find a Tech Partner or create an in-house fitness and workout app development team to build an application with BLE API integration. This step doesn’t necessarily have to be done after the first 3. You can start the development journey with a Tech Partner that offers mobile app development services from the very beginning. Generally, the earlier you partner with decent iOS and/or Android developers, the better for your project.
5. Create an application and carry out reliable BLE integrations.

Now, let’s discuss your options with a custom firmware for a BLE fitness device.

Integrating Custom BLE Fitness Devices

We can’t say that it’s a more complex process of BLE app development because we still work with code. If you have enough coding expertise yourself, an in-house development team, or a trusted Tech Partner, it shouldn’t be a problem. Let’s briefly talk about what you need for that.

Of course, your device needs a well-functioning BLE communication module. If it works well, you need a library for BLE implementation for your specific framework.

A library is a storage for prewritten code (files, functions, routines, etc.) that is used for the BLE app development service.

Developers use the collection of code for this specific framework, like when they need to make a React Native app, a Native Android app, or any other one. In the table, we’ve collected libraries for the most widespread programming languages:

If you need to integrate BLE fitness devices into your web app, the Web Bluetooth connect feature is very useful.

Then, your development team integrates BLE devices using the right library and enables communication between the device and the app. That’s it, that’s how the whole magic happens.

For a practical Android BLE app example, you can read the comprehensive guide prepared by our React Native developer, Yevhenii Burkovskyi.

Then, you need to initialize the BLE Manager. Do it only once per runtime, because the opposite action can lead to a memory leak.

Now, you can scan for available BLE devices.

In this code snippet SERVICE_UUIDS is an array of UUID-like strings that refer to BLE services. There are many conventional BLE services, like the Heart Rate Service.

If you’re implementing a custom BLE integration, you should contact the manufacturer to find out the required service and characteristics UUID (Universally Unique Identifier). SCAN_OPTIONS is an object that allows to implement a fine-grained scan, adjusting the scan behavior to the project requirements.

# 2: Connecting to a Device

When a device is found, the BLE application can connect to it and start sharing data. The method returns a promise that will be fulfilled if all conditions are met. Thus, the device must be turned on and in pairing mode. It must also be in a physical layer. If any of these conditions are not met, an error will be returned.

# 3: Discovering Services and Characteristics

Once the connection is established, the app can discover services and characteristics of the connected device. It’s a specific requirement of the react-native-ble-plx library, since without this step, you won’t be able to read or write to any characteristic.

# 4: Data Exchange

Each service has at least one characteristic: read, write, and notify. BLE-enabled apps have two-way data communication with devices by “translating” these characteristics.

You should monitor particular characteristic(s) with allowed notifications to receive data updates from the device. BLE standards have two ways to transfer data from the server to the client: notification and indication. The main difference is that the client has to confirm indications by sending a message back to the server.

The react-native-ble-plx library automatically handles both cases for us, as stated in the docs.

Then, you need to write data to a characteristic of the connected device. The data argument is a base64-represented byte array. To transform a byte array to a base64 string and vice versa, you can use the btoa and atob methods.

But since those methods are not available in the React Native BLE app development runtime out of the box, you should use an external library like base-64 or implement them yourself.

How much does a fitness app cost with BLE integration? To get an accurate estimate, you should decide on the app’s key features and consult with experienced app developers who can prepare a detailed cost breakdown of your project.

You can ease this process by choosing cross-platform development. For instance, our React Native developers use libraries like react-native-ble-plx and react-native-ble-manager. They help reduce the time and money spent on development. It’s critical when you want to bring your product to market as soon as possible.

📌 Don’t forget about fitness app UX/UI during BLE device integration.

Background Processing

Fitness devices send data all the time, even when the user's phone is locked or the app is in the background. For these situations, your app must be able to:

• Scan for BLE devices;
• Receive notifications or data streams;
• Reconnect automatically if the connection drops.

iOS needs certain settings (like background modes) and permissions to support background BLE operations. Android is more flexible, but you should ensure that your BLE connection doesn’t drain battery.

Power Efficiency

Low power consumption is a top priority during BLE app development. Most fitness devices are battery-powered. And they should work for days or even weeks on a single charge.

To ensure its power efficiency:

• Send short messages instead of long ones.
• Improve the connection frequency on the mobile app and the device.
• Use the OS's built-in power-saving features.

Simply put, you should find a balance between real-time data exchange and battery consumption.

Security

Security is one of the key parts of BLE communication. Your app deals with personal fitness data like heart rate, workout logs, or location, and your users must trust you.

You can secure BLE communication by:

• Using encryption for data transfer;
• Integrating authentication mechanisms like passkeys and numeric passcodes.

Libraries and Tools

We already gave you a list of libraries for custom BLE integration. Some libraries and tools can also simplify the development and debugging of BLE-enabled apps:

For example, you can use LightBlue Explorer and nRF Connect for peripheral simulation, BLE device scanning, and characteristics testing. These tools can help you complete the QA stage and check how your devices talk to each other before you release an app.