That ALSO, comes after this:
Although you need an iPhone to do most things with Apple Watch, you can still do several things with Apple Watch without having an iPhone in range.
Play music from a synced playlist on Apple Watch
Use the watch, alarms, timers, and the stopwatch
Keep track of your activity (stand, move, exercise) with the Activity Activity icon app
Track workouts
Display photos from synced photo albums
Use Apple Pay to make purchases. See Make purchases with Apple Pay.
Anyway, we'll all find out for ourselves when we have our watches.