Is there an integrated sleep phase alarm? So that the band recognises a light sleep phase and wakes me up in this phase instead of at a fixed time.
If there is one: Does it work well?
Yes, that does exist. It's called "smart wake-up". It can be switched on or off individually for each wake-up time. I have tried this a few times. I was usually woken up +/- 10 minutes beforehand.