Apparently, the Apple Watch https://www.youtube.com/watch?v=LPqtfC70QTU https://www.youtube.com/watch?v=LPqtfC70QTU . https://www.youtube.com/c/TheQuantifiedSci

Apparently, the Apple Watch https://www.youtube.com/watch?v=LPqtfC70QTU https://www.youtube.com/watch?v=LPqtfC70QTU . https://www.youtube.com/c/TheQuantifiedScientist https://www.youtube.com/c/TheQuantifiedScientist reviews all the sleep/heart trackers and records accuracy. He’s a professional scientist specialising in sleep research and the reviews concentrate on data/accuracy only.