If you're carrying more than one credit card in your wallet, you're now officially carrying too many. A company called Dynamics has come up with a single credit card that can reprogram itself to be any card you want it to be.
Dynamics' credit cards have managed, in one swoop, to utterly shame every credit card you've ever owned. They're not just passive pieces of plastic, they're completely computerized, with little LCD screens, LED lights, buttons, a magnetic strip that can reprogram itself, and a battery that lasts a staggering four years, all in a form factor that's just as thin and light as a traditional (i.e. old and stupid) credit card.
With all of this tech comes a bunch of features that probably should have been implemented into credit cards a long time ago. You can store multiple numbers on the same physical card, use the card's buttons to select which account you'd like to pay with, and the strip will re-magnetize itself with those numbers.
The buttons can be used as a security system, requiring you to enter a code to turn your card on while the LCD showing the card number blanks itself after a period of inactivity. And if you're super paranoid, the LCD can also be set to display dynamic security codes, ensuring that even if someone steals your card number, they won't be able to charge anything on your account.
If you want one of these cards, your best bet is to open an account with Citibank, who's currently testing them out with their customers in a pilot program.