One of the things that some people in Europe and Asia can do with their mobile phones that most of us in the US can't is pay for things using their phone. Visa and Apple have announced that they are working together to change that.
The two companies will offer a new method that will allow iPhone users to make contactless payments using the iPhone and an Apple certified hardware accessory. The accessory will likely be a case.
Using the accessory the user can pay for items with a linked Visa card wherever terminals with contactless technology is available. There is also mention of a memory card for other devices to allow the same functionality.