Google is finally opening up its near field communication payment system, Google Wallet, we reported yesterday, allowing Nexus S users on Sprint to try out contactless payments through their smartphone. Contactless payments have been something of a curiosity in the credit card industry.

Google’s new mobile phone-based Wallet service has the potential to transform the technology from its current status as a transaction turkey, to a future as a checkout champion.

Right now, Google Wallet only works with Citi-Mastercards and the Google Prepaid Card. Visa and Google announced a worldwide agreement to support the Visa payWave app, but it will still be up to the financial institutions and banks to add support.

Got a Sprint Nexus S? Ready to get to spending like some crazy time tourist? All you need to do is ensure your handset is turned on. Wallet is being rolled out to hands automatically, so no Marketplace download is necessary. As a nice little bonus, Google will kick down $10 on a Google Pre-paid card to anyone who gives Wallet a try by the end of the year.