A programmable credit card can display useful information, offer added security features, and even act as several different cards by rewriting its own magnetic strip.

Two types of programmable credit cards were unveiled this week at the DEMO conference in Santa Clara, California, by Dynamics, a startup based in Pittsburgh that's been developing the technology in stealth mode for three years. The company raised $5.7 million of funding last year.

The new cards are no bigger than the one in your wallet, and is actually slightly more flexible. It can display information at the press of a button, and can become several different cards by rewriting its own magnetic strip.

The "MultiAccount" card has two buttons on its face, each with an indicator light that can be pressed to record data to its magnetic strip. "One might switch the card to be your debit card, and the other your credit card," says Dynamics CEO Jeff Mullen. "These cards are exactly the same size and thickness of a conventional card, and the lithium-polymer battery inside can last four years under high usage. They're also fully waterproof, so you can put them through the washing machine."

The "Hidden" card features a keypad and black-and-white display for six of the digits in the card's unique number. Once the correct PIN is entered on the card's four buttons, the missing digits are filled in and the card's magnetic strip is populated with data. Both the digits and the strip become blank again after a short time. "If this card is lost, it's just dead plastic to anyone who finds it," says Mullen, who thinks it could help banks attract security-conscious consumers.

That may be true, says Avivah Litan, a Gartner analyst who researches security and technology in the financial sector, but "most card data is stolen electronically, in large volumes," she notes. As a result, banks "may prevent a few percentage points [of fraud], but it seems unlikely to be worth the investment for them."