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 said there are about 150,000 at various retail locations in the U.S. 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 in even small locations where there are PayPass terminals, including several drug stores in Harrisonburg, Va., 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 prepaid accounts to Google Wallet, but Visa didn't describe a timeline for when that function would be enabled.