Only a few cities and only on Sprint will be announced to work. And you need Android Nexus S phone to use it. It's more like a big test. And I hope it really takes off. We are some 10 years behind Japan on this. The pretty much can pay for their drinks on vending machines, tickets for trains and all kind of small payments, just by swiping their phones over a sensor. And that's for almost a decade. It's so easy.
Now this can happen here, too. Go Google!