Your iPhone is now your credit card.
The iPhone 5 may contain a Near Field Communication chip. This device allows wireless connection over small distances, which would allow apps that turn it into an e-wallet (swipe your phone over the card machine to pay) or a security key. CultofMac reports that Apple has hired an expert in NFC technology and patented quite a bit of NFC tech in the recent past.
This new chip could also allow remote computing. iPhone users would be able to hold a fair amount of desktop info and settings on their phones. It would be simple to then transfer that onto another Mac. Waving the iPhone close to a Mac could be enough to prompt the transfer. When the iPhone is removed from the new Mac, it reverts to how it had been. Here's how one source describes it:
“The system would essentially turn any Apple computer into your own — like you’re actually working on your own computer. Same settings, look, bookmarks, preferences. It would all be invisible. Your iPhone would be all you needed to unlock your Mac.”
This certainly makes sense for Apple. The Back to the Mac event stressed the near-merging of iOS and OS X, and this would be one more way to strengthen the bond between both platforms- and to make buying a Mac an even more attractive idea to millions of iOS users.