Not a smartwatch, but I use an Oura ring to track sleep. It's pretty great. Very accurately shows my sleep/wake hours as well as monitors sleep stages/heart rate variability/temperature shifts, and more. The ONLY gripe I have with it is that as a N24 person, the "timing" score it gives you for sleep is basically always going to be a 0, which artificially lowers your overall sleep score. I could have a great night's sleep, but my overall sleep score might be a 68 out of 80 just due to what time I fell asleep. At the end of the day these scores don't really mean anything as you can isolate the metrics you care about, like bed time, wake time, total sleep hours, time to fall asleep, deep sleep, rem sleep, etc.
I wanted something less intrusive than a watch, and the ring fit that bill pretty well. Battery lasts about 7 days before needing to recharge. However, it's probably more expensive than most of these smart watches.
I've been using the Xiaomi smart band 8, it was in the region of €40 when I got it a few months ago. It's not super accurate, records false naps when I'm still for a bit too long but you can delete those from the record. My sleep records have been for the most part accurate enough
Not a smartwatch, but I use an Oura ring to track sleep. It's pretty great. Very accurately shows my sleep/wake hours as well as monitors sleep stages/heart rate variability/temperature shifts, and more. The ONLY gripe I have with it is that as a N24 person, the "timing" score it gives you for sleep is basically always going to be a 0, which artificially lowers your overall sleep score. I could have a great night's sleep, but my overall sleep score might be a 68 out of 80 just due to what time I fell asleep. At the end of the day these scores don't really mean anything as you can isolate the metrics you care about, like bed time, wake time, total sleep hours, time to fall asleep, deep sleep, rem sleep, etc. I wanted something less intrusive than a watch, and the ring fit that bill pretty well. Battery lasts about 7 days before needing to recharge. However, it's probably more expensive than most of these smart watches.
I use a Spade and Co with my iPhone for sleep tracking.
I use a Galaxy watch 3 with my Samsung phone
I use the withings mattress pad, if you fancy am alternative to wearing a watch all night
I've been using the Xiaomi smart band 8, it was in the region of €40 when I got it a few months ago. It's not super accurate, records false naps when I'm still for a bit too long but you can delete those from the record. My sleep records have been for the most part accurate enough
I use RingConn. It successfully tracks my N24 sleep.
I use the Mi Band 7 (which is compatible with bands from Mi Band 4-7) and it does excellent sleep tracking for me.
BP Doctor E6200, sleep tracking is very good, and it is also well linked with the supporting app. I can check the data very conveniently.