Now if only I could carry my ID around on my iPhone I wouldn't need to carry a wallet.
Until you drop you phone and break it or it barfs on you in some other way. There was high profile case of an iPhone user who got fined over £600 because the phone died and they could not show the rail ticket to the guard on the train. She was lucky enough to get it picked up by the national press, probably knew someone.
With certain NFC transit cards, the iPhone can now emulate them even when the main OS shut down due to low battery!