Hi guy. First, sr for my English :)
Next, I have mi 4w and mi band.
So, I use to unlock the phone with miband, Bluetooth always on, of course.
In miui 4.4 or mm 7.2.8. Bluetooth almost no use battery (in battery used - security)
I try dev eu miui mm, and now miui stable 7.3.1. Bluetooth uses...