TL;DR: Without your iPhone, a GPS-only Apple Watch can still do lots for you. Track workouts, track activity, tell time (including setting alarms, timers, and using the stopwatch), play music from a synced playlist, display photos from synced albums, make purchases with Apple Pay, check heart rate, use the Breathe app, and listen to podcasts stored on Apple Watch. If your iPhone is off or out of range, the Apple Watch can still connect to known Wi-Fi networks and do several other features.