Yesterday, Google introduced the world to Google Wallet, it’s new, NFC-based, contact-free, payment system.

Not yet available to the public at large, but expected to be rolled out over the summer, Google Wallet is set to change the way we all pay for our groceries, clothes, dinners, and more.

Once Google Wallet gets rolling, consumers will be able to tap their cell phone on a sensor to make payments through their Citi MasterCard, Google Prepaid Card, and gift cards from participating merchants.

According to Google, the Google Wallet is more secure than having cards in a regular wallet, because users will be required to enter a PIN number prior to making payments. They also say that data on the phone is encrypted. However, they still advise that if a phone with Google Wallet on it is stolen, the user should call their banks and cancel the cards, just like they would if their regular wallet was stolen.

When Google Wallet launches, it will be available for use on Sprint’s Nexus S 4G by Google. It won’t work with any other phones yet. Google’s site states that “Over time, we plan on expanding support to more phones.”

As for participating stores and restaurants? Google says there will be hundreds of thousands. Some of the national chains that have signed up so far include Walgreens, Toys’R’us, Subway, Radio Shack, Macy’s, Bloomingdale’s, CVS, Sport’s Authority and more.