Gadgetbridge is an Android (4.4+) application which will allow you to use your Pebble, Mi Band, Amazfit Bip and HPlus device (and more) without the vendor's closed source application and without the need to create an account and transmit any of your data to the vendor's servers.
This is a customized version of Gadgetbridge. I added an content provider so now other applications are able to query data of XIAOMI MiBands. To do so you will have to make use of the contract class. Good luck!