The Mi Bands 3 and 4 have a new firmware update that fixes several UI-related bugs. It also introduces a first-party notebook-unlocking facility to these fitness trackers. They also now support Apple ID logins for the first time.
https://www.notebookcheck.net/Xiaomi-updates-the-Mi-Band-3-and-4-with-a-laptop-unlocking-function.459787.0.html
Thanks.
They should also make it able to work as a shutter for the phone camera.