Ars Technica's Ben Kuchera (normally their game journalist) takes a look at some smart credit card technology being shown off at CES that could allow for security on our cards or using one card for multiple accounts.:

The technology is impressive. The cards look and feel much like existing credit cards, and can be kept in your wallet and bent without harming the internal electronics. The difference is that an empty screen replaces a section of the numbers on the card's face, and you have to tap in a key using five built-in buttons before making a purchase. The LCD screen is then filled with a unique credit card number, and the magnetic strip on the back is coded with that number for use in the transaction. Once the transaction is over, the numbers leaves the face of the card, and the magnetic strip returns to its blank state.

Apparently the batteries included should function for 3 years. Could be a practical way of improving a system we have which works but is prone to abuse.