Yes, seems a good tracker for sleep/wake amounts overall-but no sleep staging (deep vs light vs REM) at all. The research study they did comparing to NPSG (gold standard; which instead, they call “Ground Truth”, in Google’s world) was not published in any journal, so no peer-review. They present graphs comparing them to “other sleep trackers” not identifying which ones-guaranteed not the Oura or even the Muse-S, nor against NPSG:
So while marginally better at sleep detection specificity, they are nearly as poor as other trackers (55%vs50%) at detecting wake after you’ve fallen asleep-most likely confusing REM sleep and Wake.
They do present Bland-Altman plots comparing their algorithm to the gold standard but those graphs are really hard to interpret.
Oh, yeah, and even though they thought they excluded sleep apnea, they included significant sleep disordered breathing AHI of 6.53 (normal < 5) oxygen desaturations to 86% (normal >90%), abnormal Total Sleep Times for in a sleep lab (~6hrs, normal >7hrs) and sleep efficiency (81%, normal >85%). All these subnormal values actually worked against them, but still, not unusual for the “normal” population with that age range.
Bottom line, if you want to have a general sense of how much or little sleep you are getting, go for it. If you want any other information, like how much REM sleep, pass.