I had a fitness tracker/wearable (Jawbone I think) that would track your sleep, and vibrate to wake you up at the best point of your sleep cycle within +/- 15 m

I had a fitness tracker/wearable (Jawbone I think) that would track your sleep, and vibrate to wake you up at the best point of your sleep cycle within +/- 15 minutes of your set alarm time. I really like the idea, but the thing would always fall off at night. Maybe I should try a new one...