Last known working firmware version: 126.96.36.199
This app currently only works with the Mi Band, and requires the main app to be installed and paired with the band - as the band is not discoverable once paired.
The app currently only works with Lollipop due to significant incompatible changes in the BLE stack, there are no immediate plans to change this.
Disclaimer: This app is in no way associated with Xiaomi. This app includes no warranty for your device, in my testing I've never bricked my band - but as I'm reverse engineering their API, it's entirely possible, albeit unlikely.
Compatibility pull requests are highly encouraged, I am currently working on compatibility with the latest firmware.