I have a Xiaomi band 2 which I bought for some 30 EUR and it also considers me asleep when playing games before I go to sleep and sometimes when watching TV as

I have a Xiaomi band 2 which I bought for some 30 EUR and it also considers me asleep when playing games before I go to sleep and sometimes when watching TV as well. Other than that it's pretty accurate, it even detects the occasional 15 steps to the toilet and back as awake time and I'm generally happy with it. It has a heart rate sensor but AFAIK you need to put some other firmware on it to use that during the night at predefined intervals. Regarding tracking sleep quality (it only has light, deep and no sleep as categories), I feel it tracks it well enough and I treat the duration of deep sleep as an upper bound (usually around 2h30). So if the band shows me little deep sleep it's almost always correct (i.e. I don't feel I slept well). If it shows lots of deep sleep I can sometime confirm and sometimes not. Of course, all this is subjective, so "sample size = 1" holds ;)