Recently I have been reverse engineering the DSB012 (AKA the SATB 4.0 A1) fitness tracker made by Silvercrest. It can be purchased for as little as $4 in Dollarama. It is supposed to sync with a phone or tablet through the ezfit app, however the app is missing from both the App Store and from Google Play. An APK download is available from apkpure but it only works on Android 7. There is no way to connect it to a computer.
This renders the device almost unusable, which seems a waste given its cool design. This is why I have been working on reverse engineering the protocol it uses to interface with the app. I am building a progressive web app which uses the Web Bluetooth API to interface with the fitness tracker. So far, my app can only measure the device’s battery level, detect when its button is pressed, show its firmware version, and send commands to the device. It is more of a proof-of-concept than a usable program.
In the future, I hope to finish reverse engineering the protocol and creating a user interface.