>Isn't "movement in bed" how all sleep monitors work?No.
The best ones monitor your brainwaves, and the best wearables monitor the next best ting, your hear rate and blood oxygen.
You can get knocked out by drugs, alcohol or just die in your sleep from apnea so you'll not move around in bed and your bed motion sensors are useless.
You need to tap into the body's vital signs to know your sleep stages accurately, especially REM.
