Here in Canada, we have "contactless" payments on the major credit and debit cards. When it's time to pay, you just tap your card on the reader and it's done().

NFC payments using a phone would add a few more steps, so I think that the wallet and card is going to win out for me. It would be very hard to get it much simpler than it is right now.

() There are limits. My MasterCard, for example, will let me make contactless payments up to a total of $50. At that point it will require me to make a Chip&Pin transaction in order to reset the $50. When this happens the reader will just say "Insert Chip" or something.