Take MasterCard: its MasterPass software enables retailers to create their own apps for customers to pay for goods - using QR codes, Near Field Communication (NFC) technology, mobile credit card readers (like Square) or MasterCard's proprietary MasterPass wallet.
Visa's just joined forces with point-of-sale company ROAM, who not only creates checkout terminals in stores, but whose technology helps turn phones into checkout counters. Visa hopes this will make it easier to get its mobile payment technology, Visa Ready, into physical stores.
PayPal's answer to Square's card reader technology is PayPal Here, which has been available in the U.S. for a year, and has recently launched in Europe. PayPal Here works on iPhone and Android platforms and accepts credit cards, checks, cash, or a PayPal wallet.
It's hard to deny the convenience of ditching the wallet for the gadget that is permanently attached to your hand anyway. But nay-sayers have a point: do you really want to entrust your purchasing capabilities to a device whose battery could run out, leaving you stranded?