Leander Kahney, Cult of Mac:
Thanks to sensors on the Apple Watchâ€™s back, the device can tell when itâ€™s being worn and when it has been taken off. When you first put the watch on, you must enter a code. When the watch is removed from your wrist, the watch locks itself and canâ€™t be used for payments unless the code is entered again.
Guess you can’t wear the Apple Watch loose?