See Garmin Health Announces Sleep Study Results [1].
I used a Zeo [2] mobile for a few years and I thought I had a good feel for what my sleep cycles tended to look like.
I bought a Garmin VivoSmart last Black Friday mostly to try the SpO2 and sleep tracking. I shared your skepticism but, anecdotally, the sleep cycles are as good as what I would get from Zeo.
Hmm... 70% agreement in an unpublished study funded by the company vs a device that is itself maybe 90% agreement with lab PSG. Better than I expected, but I wonder if it is just due to many sleepers having quite predictable stages. "Figure 4 shows the worst result of the cohort (55 of 55), with an accuracy of 49.9%. Note that this user self-reported having a sleep disorder."
> I wonder if it is just due to many sleepers having quite predictable stages
That is what I wondered. The Garmin reports my deep sleep in ways that don't match predictable patterns and do approximate times of random events like being woken by animal noises or sirens. Its much better than I expected and I can see it getting much better with the incorporation of additional sensor/external data.
I used a Zeo [2] mobile for a few years and I thought I had a good feel for what my sleep cycles tended to look like.
I bought a Garmin VivoSmart last Black Friday mostly to try the SpO2 and sleep tracking. I shared your skepticism but, anecdotally, the sleep cycles are as good as what I would get from Zeo.
[1] https://www.garmin.com/en-US/blog/health/garmin-health-annou...
[2] https://en.m.wikipedia.org/wiki/Zeo,_Inc.