Whether they're called PayPass, ExpressPay or Blink, contactless credit cards are the newest way to buy with plastic.

You just wave them in front of a specially-equipped cash register and your bill is charged to your account. It's a little quicker and easier than swiping your card through a magnetic reader.

Do you need one right now? Probably not.

But you'll almost certainly want a high-tech card like this sometime in the future.

Some amazing new uses could make life easier and, despite what you may have heard, thieves can't steal your identity and account number right out of your wallet.

Wave-and-pay cards have a built-in computer chip and antenna that allow them to respond to radio waves from a card reader.

They're intended to help you make quick purchases of $25 or less. You can always spend more than that, but it requires the usual swiping and signing.

That's why most wave-and-pay card readers are being installed in convenience stores, fast-food restaurants, drug stores and movie theaters.

American Express claims that paying for morning coffee with a contactless card is 63% faster than paying with cash. But most of those wave-and-pay transactions arenâ??t much quicker or easier than swiping a conventional credit card.

The ability to pay tolls or train fares would be a far more compelling reason to get a contactless card.

Sam Wang, the vice president of public affairs for Citigroup Global Consumer Group, says it's allowing New Yorkers to wave-and-pay their way through subway turnstiles at some stations.

American Express is testing contactless cards on buses that take skiers from Salt Lake City to nearby mountains. MasterCard is trying the technology at tollbooths on the Ohio Turnpike.

With more than 11 million contactless cards now in use, there's an understandable concern that crooks could use portable card readers to steal account numbers right out of our pockets or purses.

But the credit card companies say that's not possible because the number your card gives out when it responds to a wave-and-pay card reader is a different from your regular account number.

If someone uses a stolen wave-and-pay number to make counterfeit credit cards or buy something over the Internet, the verification system recognizes that and rejects the transaction.

"By only transmitting the unique code, the credit card account number is protected," says Molly Faust, a spokeswoman for American Express.

If the credit card companies are wrong we'll undoubtedly hear about it as contactless cards become more common and ID thieves inevitably try to crack their security systems.

A more immediate concern might be the effect wave-and-pay cards have on our spending.

"It's just too easy to rack up charges," says Mindy Weinstein, a credit counselor at the Financial Victory Institute in Fullerton, Calif. And if you don't get a receipt it's even easier to lose track of how much you've bought.

"Just $5 a week or so can add up," Weinstein says. "If you carry a balance and then start paying interest on those purchases they could get very expensive."

Bottom line: When a contactless card can improve your life in a substantial way, go ahead and get one. But you don't need one to save a few seconds in the coffee line.

By Carolyn Siegel

Interest.com Associate Editor

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