Fitbit's update for the Charge 4 will help you wake up at the "best time" - SoyaCincau
Fitbit Charge 4 (and Charge 3) tips and features: How to use your new tracker - Wareable
fitbit on Twitter: "Smart Wake activates a gentle buzz on your wrist during your lightest sleep stage so you can really take flight when it's time to rise. Goodbye, groggy. Hello, energy. #
Fitbit Charge 5 vs Fitbit Charge 4: Which fitness tracker is right for you? | TechRadar