Requenes.com

The big problem is compatibility with existing systems. The card has to work with whatever credit-card-accepting systems are in the field. Ideally, no new hardware should have to be deployed to take advantage of all the features of the card. Frankly, I haven't figured out a way to get around these issues. My universal credit card idea is not fully developed. I include it in this collection as an example of a probable dead end.

The last time I thought about it, the idea was as follows. A slim case fits over a plastic card. The case can write information to the card's magnetic strip when you remove the card. The case has a membrane keypad on it. Using the function keys on the case, you program the account that you want the card to represent. After you remove the card from the case, you use it like an ordinary credit card.

If so desired, the case could require a passcode to enable the card. Removing the card without the correct passcode would erase the magnetic strip. Perhaps you could even program the amount of money that you want the card to "contain."

I'm sure there are many flaws with this idea. For one, the card doesn't have the raised account numbers that are needed by some credit card processing devices.