XDA user Mauronofrio decided to create a fast and secure program to simplify modding on these watches. At this moment only the Amazfit Pace is supported, when there are more guide on Amazfit Stratos he will upgrade this tool. Remember to unlock your Amazfit bootloader you always need of unlock code from https://unlockamazfit.com/
Source: [TOOL][PACE/STRATOS]Huami AMAZFIT Tool (Unlock|Rebooter|APK Installer|Mod Installer)