10 Apps That Will Turn Your Apple Watch Into a Sleep Tracker

Cost: free; premium subscription is $7 per month

From the moment your head hits the pillow, Pillow starts tracking the awake, REM, light-sleep, and deep-sleep phases of your sleep cycle and analyzes them alongside your heart rate. The app then compiles your nightly sleep data into a color-coded infographic, letting you visualize and pinpoint where you can improve your sleep patterns.