Men's Health | 13.10.2026 00:54SMART RINGS, BANDS, ANDwatches will all tell you how you slept last night, down to your heart-rate variability (HRV) and blood oxygen. They track how long it took you to nod off, how often you stirred, and how much of the night you spent in deep sleep and REM. It’s a remarkable amount of insight for a device that sits on your wrist or finger all night.
