Sleep Stage Sensor Data

I’m looking into a galaxy watch app that tracks sleep stages in realtime (or at least as the data is made available per the sensors), but I’ve found a few threads saying that sleep stages aren’t actually tracked by some watches, and that data calculated by samsung health after the fact, and that the only data available via the API is whether the user is awake, asleep, or unknown. I can’t seem to find a definitive answer one way or another if sleep stage data is accessible via the sensor api in realtime on some devices, and if so, which devices those are. Can anyone point me in the right direction?


The G’night Sleep Smart says it does that and the reviews are fairly good. I think that it uses it’s own algorithm to determine sleep cycles.

Samsung Developer Program