Google officially launched its Google Wallet application for NFC-ready Nexus S 4G phone users in the US.
The application launches initially for Citi MasterCard credit card holders, but Google also said that Visa, Discover and American Express will be able to add their cards to future versions of Google Wallet.
The application, first announced in May, was described in a Google blog.
Google said it would begin rolling out Google Wallet to Nexus S customers through an over-the-air update. Customers need to look for the "Wallet" app on the phone. A two minute video demo of the app is included.
"This is still just the beginning, and while we're excited about this first step, we look forward to bringing Google Wallet to more phones in the future," said Osama Bedier, vice president of payments at Google.
The Google Wallet works with MasterCard PayPass payment terminals with the transaction enabled via wireless Near Field Communication (NFC) technology. Users must enter a PIN in the application to enable each payment, which is done by passing the Nexus S phone close to the payment terminal.
While Google says in its materials that there are "hundreds of thousands" of PayPass terminals, a MasterCard representative at a sneak peek last week said there are about 150,000 at various retail locations in the US. Some of the terminals still need software upgrades to work with the phones.
Some Google officials said the Google Wallet would launch in San Francisco and New York initially, but the Google Wallet site lists many smaller locations where there are PayPass terminals, including several drug stores, a college town of about 40,000.
Visa said in a separate statement that its has licensed Google to use Visa's PayWave technology, used in "hundreds of thousands" terminals in retail locations worldwide.
Visa account holders will be able to use their Visa accounts to add their credit, debit and pre-paid accounts to Google Wallet, but Visa didn't describe a timeline for when that function would be enabled.
Google said it will allow users to add any bank card to a Google Prepaid Card and they will receive $10 (£6) to try the service. The card is virtual, not a physical card, and while Google said it is available, there appeared to be no place to create the pre-paid card.
Google hasn't given any hint as to when Google Wallet might be rolled out in any other territories.