Using mobile devices to make payments will be inevitable, thus all the different companies trying to figure out how to do this correctly especially the peer to peer aspect. Paypal and Venmo are the ones that come to mind. Square cash is a new service created by Square that uses the "$" tag with a handle you create in order go get paid. Watch the video to see how they envision this to work.
Let me put it this way, it'll make payments that much easier at conventions when a customer doesn't have cash or credit card on hand to pay for goods, but has their phone.