Sleep as Android does not have direct integration with Mi Bands and Amazfit, because the API necessary for integration is not open. But thanks to the Tools & MiBand and Tools & Amazfit app, you can use some devices with Sleep app. Tools & Mi Band and Tools & Amazfit are developed by Tools & Wearables Ltd..
This is a companion discussion topic for the original entry at https://docs.sleep.urbandroid.org//devices/tools.html