> Have you found any good sleep trackers that aren't wrist-based? Any recommendations?

Unfortunately not. :(

Whoever can crack that nut is going to be very wealthy.

I am using the Dreem 2 (dreem.com, use my referral code for a discount: UEXBFMANU). I do not have a certified reference device but those aspects of the recordings that I can assess (start and end of sleep, awakenings, onset of sleep, position) match my experience and are more accurate than the other devices I am using (Withings Sleep, Garmin Fenix 3). There are several in depth reviews on the web comparing the device output with state of the art polysomnogram recordings.

I'm dying to test Dreem 2, but having burned by so many gadgets that went out of business, including a very similar Zeo Sleep Tracker[1] almost 10 years ago, I'll hold for a while more to see if the company will survive.

Their recent research comparing Dreem to a regular PSG [2] is pretty impressive, but I'm skeptical of their business model, and am concerned they won't survive for long.

[1] https://www.mobihealthnews.com/20772/exclusive-sleep-coach-c...

[2] https://www.biorxiv.org/content/biorxiv/early/2019/06/10/662...

Peter Attia recommends Oura Ring.

https://peterattiamd.com/members/discounts/