How to Integrate BLE-Based Fitness Devices into your App

Smart fitness devices became users’ best friends after the COVID-19 pandemic boosted the switch of the world to remote working, studying, negotiating, you name it. Fitness wasn’t an exception and a lot of people started working out using various smart devices combined with an application.

January typically witnesses a seasonal spike in downloads of fitness and workout mobile applications. According to Statista, in January 2020, there were approximately 16.3 million downloads of top fitness and workout apps, marking an impressive 80 percent surge from the previous year.

However, the trend seems to have stabilized in the last two years, with downloads of these popular mobile fitness apps showing a slower rate of growth. In January 2024, the foremost mobile fitness and workout apps registered nearly 14 million downloads globally, reflecting trends in the fitness app retention rate.

Companies had to dynamically adjust to current market needs and offer users a solution. For a lot of companies, the solution was a BLE-based fitness device paired up with a dedicated app.

The BLE-based devices are extremely popular in the fitness industry exactly for these qualities — 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.

Let’s start with some technical details. Firstly, the data transfer between two BLE-enabled devices is regulated by GATT. It stands for Generic ATTribute Profile and defines that two devices with an exclusive connection communicate using the Services and Characteristics concepts. Take a look at the following scheme and we’ll unpack it right after:

• GATT Server is divided into several services. For example, there 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 basically 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 — 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 essential part is the difference between central and peripheral devices. To begin with, central devices are the ones that initiate the connection, peripheral 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, your user’s phone (central) can be connected to a fitness band, a heart rate ring, and smart dumbbells (peripherals) simultaneously, while each one of these devices can be connected to a single iOS or Android device.

However, these are only some general rules. With a proper configuration, a device can be both at the same time, which enables peripheral devices to several connections to different central devices. Plus, the number of connections is technically unlimited, but in practice, there’s always a certain limit. For example, 20 connections are something totally reachable.

There are also such terms as GATT Client and Server, that are often compared with central and peripheral roles, but these are dissimilar concepts. The difference is that client and server terms refer to how the data flow and storage are managed, while central and peripheral roles define the connectivity structure.

The Client/Server relationship itself is pretty simple. Client devices access the data, while Servers are responsible for storing and providing access.

BLE connectivity capabilities can be further extended and enhanced with the
Mesh Bluetooth technology. It enables devices to form a mesh network, allowing them to communicate with each other over longer distances by relaying messages through intermediate nodes.

Bluetooth SIG defines that even if a device is out of direct range of a central device, it can still communicate as long as there’re other devices within range to relay the message.

Mesh technology can be also implemented in fitness apps paired with BLE-enabled devices, such as heart rate sensors, smart scales, and exercise equipment. This allows for seamless data synchronization, higher transmission power, and analysis across multiple devices, enhancing the user experience and enabling more comprehensive fitness tracking.

If you’d like to learn more technical details about Bluetooth technology and BLE intergrations, feel free to follow the link to our article fully dedicated to BLE devices:

BLE vs Classic Bluetooth

Since we’ve already talked about what BLE is, let’s briefly talk about Bluetooth Classic. It’s also a wireless network that establishes a connection between 2 Bluetooth devices (think about wireless earphones or speakers). Its main function is exchanging big amounts of data at close distances.

The main significant Bluetooth vs BLE difference is that BLE is designed for smaller amounts of data transfers with lower battery consumption. The battery service in BLE fitness devices can last for years. Thus, this option is much cheaper, compared to building Bluetooth-based devices. Bluetooth, on the contrary, is more pricey because it works with “heavier” data and requires more maintenance in terms of battery level.

Because of this difference, Bluetooth Low Energy is much more widespread in the fitness industry. It allows companies to provide their customers with user-friendly ready-to-use devices at a relatively low cost.

Another important difference is that Bluetooth Classic has an active connection for a limited period of time (from a couple of 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 take a look at how BLE integrations can be used in the fitness industry.

Bluetooth Low Energy Uses Cases in the Fitness Industry

Fitness bands and smartwatches are something that most of us know, have, or regularly use — this is one of the most widespread BLE integration use cases. However, the industry, including when you develop a mental health app, goes far beyond that and embraces a lot of fascinating IoT (Internet of Things) technologies. Now, a BLE device acting as a bridge between the physical object and the digital world enables seamless communication and data exchange.

Smart Mats

BLE-based smart mats for exercise and yoga are able to analyze posture and exercise positions, provide users with recommendations on how to improve them, count the repetition of the exercise, keep a record of workouts to overview progress, etc.

When it comes to providers of such mats, the market is full of them: YogiFi, SmartMat, Otari, and many others. The basic functionality is pretty much the same, but some providers offer additional features that surely increase costs. Otari, for example, has an AI-based camera that oversees people while exercising in real-time and provides voice-based instructions.

If you’d like to learn more about building yoga applications, we have an article about it, where we review the whole development process in detail:

Smart Glasses & Traning for Olympics

There’s a start-up called Solos that offers smart glasses to their customers. Solos glasses were used by cyclists for training for the Olympic Games.

These glasses are BLE-based technology using Augment Reality features that are able to provide athletes with real-time data like speed, distance, cadence, calory count, heart rate, etc. Additionally, it can communicate with such popular cycling apps as Strava, MapMyRide, and TrainingPeaks.

Users can actually see the data in front of their eyes while wearing glasses, thanks to an intuitive interface. To see more visual content and videos on how the Solos are used, you can visit their Kickstarter page.

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 & marketing services. Namely, you can use Beacons for such purposes.

Beacons are Bluetooth Low Energy devices that constantly radiate radio waves that other BLE- or Bluetooth-enabled devices can see. Their main purpose is “taking over” the device they communicate with to perform specific actions — open a webpage, start an app, launch a marketing campaign, etc.

Basically, when users’ devices get into a beacon’s range, they do what beacons ask them to, meaning you can easily use them for business purposes.

However, this functionality relies on location permission, which users may not always grant, limiting the effectiveness of beacon-based strategies. Obtaining the necessary location permission is crucial for ensuring seamless BLE integration and optimal performance of beacon technology within your business operations.

Let’s take a look at use cases:

All of that can be done even if you don’t have an app. However, in case you do, you get access to much more detailed customer information. It allows you to personalize your campaigns better and generally adjust your approach to clients’ needs.

For fitness app developers involved in BLE development, the chances that their hardware provider won’t offer an SDK/API as part of the cooperation are minimal. In case that happens, they’ll most likely refer you to their partners who have solutions for their products specifically.

So, generally, the steps you should follow when opting for a partnership with a third-party fitness device provider are as follows:

• Think about what device(s) you’re looking for and start exploring your provider options.
• Find a hardware provider so as to offer users a full-on solution that’s ready for usage the moment they get it.
• Check if the provider has an SDK/API. If yes, make sure they meet your business needs. For example, an API to establish the connection between a fitness band and an Android phone app is totally irrelevant to you if you’re building an iOS application. If they don’t, think about alternatives.
• Find a Tech Partner or create an in-house development team to build an application with BLE API integration. This step doesn’t necessarily have to be done after the first 2. You can start the development journey with a Tech Partner by your side. Generally, the earlier you partner with decent iOS and/or Android developers, the better it is for your project.
• Create an application and carry out the appropriate BLE integrations.

Now, let’s take a look at what options there are for you in case you have a custom firmware of BLE fitness device.

Integrating Custom BLE Fitness Devices

We can’t say that it’s much more complex because practically, it’s still working with code. It’s not like a person without coding knowledge would be able to use API to perform the integration. So, 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 module. If it works well, you need a library for BLE implementation for your specific framework. First, let’s cover what a library for a framework is.

Long story short, a library is a storage for prewritten code (files, functions, routines, etc.) that can be used for the development of applications and their integration with other applications, services, devices, etc.

So, a library for a framework implies the collection of code for this specific framework (React Native, Native Android, or any other one). In the following table, we’ve collected libraries for the most widespread programming languages:

Then, your development team performs the integration using the corresponding library and enables communication between the device and the app. That’s it, that’s how the whole magic happens.

The way we described it now might create an impression that the job is in fact pretty easy but don’t get us wrong — for it to be “easy”, developers need to have a high level of expertise.

Configuring BLE Connections in React Native

If you're eager to gain hands-on experience with BLE integrations, this section is for you. Our developer, Andrian Yarotskyi, will show you a practical example of BLE connection integration using React Native and react-native-ble-plx.

Lets’ go! 🚀

1. Import the required module.

2. Initialize the BLE Manager. It’s important to do it only once per runtime, since the opposite action can lead to a memory leak.

3. Scan for available BLE devices.

In this code snippet SERVICE_UUIDS is an array of UUID-like strings that refer to BLE services, defined in Bluetooth Core Specification. There are many conventional BLE services like Heart Rate Service, but if you’re implementing a custom protocol, then you’ll have to collaborate with the manufacturer to find out the required service and characteristics UUIDs (Universally Unique Identifier). SCAN_OPTIONS is an object that allows to implement a fine-grained scan, adjusting the scan behavior to the project requirements.

4. Connect to a specific BLE device. The method returns a promise that will resolve if all conditions are met: the device is turned on, is in pairing mode and is in a physical layer, and otherwise will reject with an error.

5. Discover services and characteristics of the connected device. It is a specific requirement of this library, since without this step you won’t be able to read or write to any characteristic.

Each service has at least one characteristic. Characteristics allow one or more of these actions or none of them: read, write and notify. To find out which characteristics you need to use for the communication with you device, you’ll need to contact the manufacturer or research the service documentation.

6. Monitor particular characteristic(s) with allowed notifications to receive data updates from the device. BLE standards define two ways to transfer data from the server to the client: notification and indication. The main difference is that indications must be confirmed by the client by sending a message back to the server. The library automatically handles both cases for us, as stated in the docs.

7. 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 btoa and atob methods. But since those methods are not available in React Native runtime out of the box, you’ll have to use an external library like base-64 or implement them yourself.

But what is a protocol after all? Basically, you can think about it as a language that the device “speaks” and that has to be used for communication. The fact of devices being based on the same wireless network (in our case, BLE) doesn’t mean, however, that they’ll have the same protocols. In addition, each device on the network has a unique Media Access Control (MAC) address, serving as its distinct identifier within the network system.

So, the challenge comes when we have several BLE-based elliptical machines, for example, that all have different protocols for integration and communication. In other words, they all perceive 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 3 lines of code sent in a specific order with a predefined holdup.

The same thing works for communication itself. If we want to change the speed of some 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 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 throw errors.

What’s even more exciting 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 so you start trying out every possibility.

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 are formed. It’s not like out of 1M fitness bands, each one of them has different protocols.

Once BLE device returns responses to developers in accordance with a certain protocol, they’re able to define its structure and easily communicate with the device. This allows them to create React Native fitness apps that facilitate seamless communication across various BLE devices.