iWatch Series 9 is Always-On Retina display Up to 2000 nits, More features: Speaker, Microphone, Side button, Emergency SOS: International emergency calling, Fall Detection and Crash Detection. Sensors: Blood oxygen sensor and app, High and low heart rate notifications Footnote, Electrical heart sensor and ECG app Footnote 4, Third-generation optical heart sensor, Irregular rhythm notifications Footnote, Sleep stages, Temperature, sensing Footnote 6, Compass with Waypoints and Backtrack, Always-on altimeter, High-g accelerometer, Ambient light sensor. Built-in rechargeable lithium-ion battery, USB-C magnetic fast charging cable Up to 18 hours normal use, Up to 36 hours in Low Power Mode. Safety: International emergency calling, Fall Detection. 39.0g