The iCache (from 2007) had an interesting solution to the security issue that everyone is mentioning:

[A]ctivate the device with a fingerprint on its biometric strip, scroll through a list of cards on its screen and choose one. Out pops a plastic card with a magnetic stripe, temporarily loaded with the chosen card's data. Just swipe the card and pop it back into the iCache. After one use, the information on the card disappears.

http://money.cnn.com/2007/08/23/technology/one_credit_card.b...

Although I'm not sure if the information disappears after the swipe or after it's loaded back into its case.