I have tested the new Auto Sleep Tracking for two nights.
First night with MiBand and Tools to track activity and HR, second night with Sleep Phaser to track activity and Breath Monitor.
On both nights the sleep tracking started way early, probably because I did lay down in bed, but I read for almost an hour.
Also on both nights, the bluetooth connectivity failed, and I had no activity tracking, no HR, nor Breath monitoring.
I will keep on manual for now, as without any extra monitoring, SaA is almost like just any other alarm app.
My advice to the devs would be to concentrate on the connectivity, and not functionality like Auto Sleep Tracking. The latter is somewhat fancy, but hardly neccessary, and way below connectivity as priority.