Google today announced and demoed Google Wallet, an app that turns your phone into your wallet. The company has partnered with Citi, MasterCard, First Data, and Sprint to make it possible for you to tap, pay, and save using your phone with Near Field Communication (NFC).

Google says it is building an open commerce ecosystem, and will develop APIs to enable integration with numerous partners. Unfortunately, Google Wallet is only initially compatible with the Nexus S 4G on Sprint. The search giant does not have a release date for Google Wallet other than "soon."

Although we've known Google has been interested in NFC technology for a long time now, it was confirmed with the release of Android 2.3 (codenamed Gingerbread) late last year. Solid details around Google's mobile payment platform leaked two months ago, and now it's finally official.

Google Wallet is supposed to make it easier for consumers to pay for and save on the goods they want, while giving merchants more ways to offer coupons and loyalty programs to their customers. Oh, and Google also claims it bridges the gap between online and offline commerce.

At first, Google Wallet will only support Citi MasterCard and a Google Prepaid Card, which you'll be able to fund with another payment card. This means you'll be able to tap your phone to pay wherever MasterCard PayPass is accepted. Google Wallet will also sync your Google Offers, which you'll be able to redeem via NFC at participating SingleTap merchants, or by showing the barcode as you check out.

The mobile app will be able to store your credit cards, offers, loyalty cards, and gift cards, without the bulk or additional weight. When you tap to pay, your phone will also automatically redeem offers and earn loyalty points for you. Google hopes the app will one day store things like boarding passes, tickets, ID, and keys.

Follow-up read: PayPal sues Google, former execs over Google Wallet