Google's mobile payments service, which allows you to pay for goods at the cash register merely by holding your smartphone close to a sensor, is getting its official rollout today. Currently, however, only Nexus S 4G owners (a phone that is only available on Sprint) can use the service, and it's only compatible with Visa cards and Citi Mastercards.

Google Wallet is the latest step in a movement to take physical credit cards out of the payments equation using newer technology. We wrote about Near Field Communication, the technology that makes many such mobile payment services possible, back in April.