Test run: Google Wallet's tap-and-pay system is simple

— -- The other day while buying Tic Tacs at my neighborhood CVS Pharmacy, I didn't pull cash or a credit card out of my wallet. Instead, I paid with a Nexus S smartphone from Sprint. Moments after the clerk rang up the purchase, I placed the back of an Android handset against the point of sale terminal and heard a friendly beep signifying that I had successfully used the phone to pay. The transaction took just seconds.

I've been checking out Google Wallet, the mobile payment app that can transform your cellphone into a digital wallet. On Monday, the search giant began rolling out the app to customers who own the Nexus S through an over-the-air software update. Google had been running Wallet field trials in New York and San Francisco, after first unveiling the pay-by-cellphone venture last spring. I conducted my own tests in Silicon Valley, Manhattan and northern New Jersey.

The pitch to consumers is convenience: an app that promises to help save time and, through loyalty rewards and digital coupons, money. You can store and sync up redeemable Google discount offers inside the Wallet.

I've used the Nexus S to pay at 7-Eleven and Subway, as well from the back seat of a taxicab. The tap-and-pay process is simple. The phone incorporates Near Field Communications or NFC, a short-range wireless technology that makes secure transactions possible.

The Google Wallet app on my test phone was funded by a prepaid Google debit card. Google is encouraging usage, for the time being, by issuing a $10 credit on the card. You can add to the total via any plastic credit card, starting at a $20 minimum. Citi MasterCard holders can use a digital replica of that card. (Don't worry, the full account number isn't displayed.) Eventually you'll be able to use other credit cards. You'll also be able to add favorite loyalty and gift cards to the app. Initially, that feature is limited to American Eagle Outfitters.

For now you can make "tap-and-go" payments at merchants who accept the MasterCard PayPass Network. There are some 140,000 PayPass locations in the U.S., and Google includes a PayPass finder inside the app. Google also has announced licensing arrangements with Visa, Discover and American Express and will add those payment networks to Google Wallet. (Google won't disclose timing.)

Acceptance will take time

Of course, Google Wallet and other initiatives to turn your cellphone into a digital billfold are in their earliest stages. People have paid with cold cash or plastic for generations. Educating the public and merchants about mobile payments will take time.

Google must also make the Wallet app available to other handsets. For the moment, Sprint's Nexus S is the only phone capable of exploiting the Wallet service, though more NFC-capable devices are coming.

And while Google Wallet arguably represents the most ambitious mobile payment initiative to date, it isn't the only one. The ISIS network, formed by the wireless carriers AT&T, T-Mobile and Verizon Wireless, is cooking up its own digital wallet. I already buy coffee from time to time with a prepaid Starbucks card app on my iPhone. I've also tried the free Card Case app from start-up Square. Intuit and PayPal are also in the game. (Not all these efforts involve NFC technology.)