Battery life: up to 7 days.
Compatibility: Works with iOS and Android.
Built-in GPS: With built-in GPS, leave your phone behind and explore nature with pace and distance on your tracker and see a workout intensity map that shows your route and effort in the app when you’re done.
ACTIVE ZONE MINUTES – This feature will alert you which heart rate zone you are in so you can see if you are working hard enough to achieve your goals.
SLEEP MONITOR & SCORE: Charge 4 tracks your time in light, deep and REM sleep stages and gives you night sleep monitoring in the app, so you can better understand your sleep quality and work for a better rest.
Details: Fitness-Tracker Fitbit Charge 4