Every other smart ring gave up the display; Casio kept it. The CRW-H001 tracks heart rate, blood oxygen, temperature and sleep like an Oura, and still shows the time on a real LCD, with a stopwatch, on a band of about 19 grams. Two honest limits: it is sold in China only, at around $295, and the battery is rated for roughly two years before the whole ring goes back for a new one.