Apple Watch Display Type: Always-On Retina display Battery life: Up to 18 hours Features: Blood Oxygen app | ECG app | High and low heart rate notifications | Irregular rhythm notification | Temperature sensing | Cycle tracking with retrospective ovulation estimates | Emergency SOS | International emergency calling | Fall Detection | Crash Detection | High-g accelerometer | Gyroscope | Compass Backtrack | Redesigned Compass app with multiple views | Compass Waypoints and Backtrack | GPS | Always-on altimeter