One thing that I've always imagined but haven't heard much in these discussions is the real potential behind the Apple Watch being the near-magical NFC interactions that could be achieved with its position on the body. For example, paying for groceries, opening locked doors, starting cars, etc. I feel that someone would only need to see a Watch user wave their hand and magically do something once before wanting that same "power".
For cars that problem has been solved for several years--keyless entry / ignition is pretty common these days (with the added advantage that your key lasts for years without charging and you can give it to someone).
