Google has launched Google Wallet today, an Android app that turns your smartphone into a mobile payment system. The company announced the service in May and 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).

The service appears to already be active in some markets. GigaOm snapped a photo of a Google Wallet-enabled pay station at a coffee shop in San Francisco earlier today. PCMag found a similar terminal at a local American Eagle store, although this unit lacked the Google branding.

Last week Google posted a teaser video for Google Wallet featuring George Costanza from the popular 90s sitcom Seinfeld. In the short, George attempts to stuff a note about the service into his own overflowing wallet which promptly explodes, sending receipts and other notes flying through the air. The clip ends with the phrase "Goodbye, wallet. The phone will take it from here."

Mastercard held a press event in New York City last week to show off Google Wallet, which was expected to launch "this month," according to CNET. As of writing, only the Google Nexus S 4G on Sprint will be compatible with the service but other NFC-enabled smartphones will be added to the lineup soon.

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.

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.