Fingerprint module.
And the next obvious step after making your phone more valuable than your credit card is to add a fingerprint module so other people can't use it (without stealing your phone and chopping off parts of your body).
Except some tosser probably patented it as a novel and new idea, and is sitting on the patent waiting for lots of cash from mobile phone makers.
Why don't they make a new credit card system called chip'n'print, where the cards have built in fingerprint readers whilst they're at it, and they'd still manage to mess up the design by failing to encrypt something important.
I'm off down the patent office.