anty on Nostr: There are so many wearables out there that track sleep-stages. Why are there no ...

There are so many wearables out there that track sleep-stages.

Why are there no papers on how to detect falling asleep and waking up?

It seems to be all guesswork based on accelerometer data and heart rate. Which doesn't seem to be enough to be "good enough" from what I can determine.

Why is this not a solved problem yet?