The Google Wallet limitation of only accepting Mastercard accounts has quickly become a thing of the past. Visa, which has more debit, credit, and prepaid card customers than any of its competitors, has come forward with support for Google's flagship NFC app, less than 24 hours after the app went live.
Google Wallet allows users to take their phone to a store and tap it on a credit card terminal to pay for their order. There is no need for a physical credit card.
Of course, the limitations right now exclude the vast majority of consumers. NFC technology is built into phone hardware, not software. As such, there is only one phone right now that supports Google Wallet - the Nexus S.
Additionally, the majority of retailers still don't have NFC-compatible terminals. NFC has been around for a few years - if you've ever "tapped" your credit card to pay for a purchase, it's the exact same technology.
Visa calls it Paywave, Mastercard calls it Paypass, Discover calls it Zip, and American Express calls it ExpressPay, but they're all the same thing.
Surely Discover and Amex will come on board soon, but for now, with Visa and Mastercard supporting it, mobile NFC payments are finally here. Expect this to be a trend that picks up quickly over the next couple years.