He gets into the "there's an app for that" mindset.
Limiting factor there is having to get the iDevice out, turn it on, exit whatever app it was on, find the app, start the app, wait for the app to start, then do whatever is needed to approve the transaction. This must be simplified as far as possible; yes none of it is difficult, but to win it must be easier than a credit card's "open wallet, find card, grab card, swipe card[, sign here]" model. I don't know much about the state of the art in POS transactions, but do know to beat using my CC it must be no more than "grab device, wave near target[, clerk verifies picture]".