Google has announced the availability of Google Wallet for the Sprint Nexus S 4G:

“Google Wallet has been designed for an open commerce ecosystem. It will eventually hold many if not all of the cards you keep in your leather wallet today.”

“And because Google Wallet is a mobile app, it will be able to do more than a regular wallet ever could, like storing thousands of payment cards and Google Offers but without the bulk. Eventually your loyalty cards, gift cards, receipts, boarding passes, tickets, even your keys will be seamlessly synced to your Google Wallet. And every offer and loyalty point will be redeemed automatically with a single tap via NFC”

More information: Google Wallet.