On: Arduino in the size of a AA battery

[tmuir]

You can make custom services and characteristics.

The nice thing about standard services is that 3rd party apps that know how to interact with those services can work out of the box.

[mschuster91 → tmuir]

Nope. Mi Bands (fitness trackers by Xiaomi), for example, use some weird scheme until you can access the heartbeat sensor.

DRM and obfuscation is even present in these devices -...-

[tmuir → mschuster91]

Well, there's certainly no requirement to adhere to in terms of access. Apple's HomeKit runs on BLE but has its own layers of pairing and encryption.

I'll agree though that you are more likely to find compatibility on a development board level than in a commercial product.