Press kit

Apple Watch tracks sleep stages in detail, but Apple's own alarm still rings at a fixed time; there is no smart wake anywhere in the system. RemWake fills that gap. It reads heart rate and movement to find a moment when you are already surfacing, wakes you then, and falls back to a guaranteed alarm at your set time if no such moment appears. On Apple Watch it sleeps until the window opens and only senses for the last half hour, which keeps the battery cost small; on iPhone it can read movement across the whole night from the mattress. Run both and they hand off to each other, so you get a long window and still wake to a buzz rather than a noise.

The reason timing matters is sleep inertia: the grogginess after waking, which typically lasts 15–60 minutes and depends heavily on which sleep stage the alarm interrupts. In one study, people woken from deep sleep showed around a 41% drop in performance, while those woken from light sleep performed about as well as people who were already awake.