It works by letting you take a picture of the credit card using your phone's built-in camera. This is the same technology many banks are now using to process checks on the fly. Then you enter the expiration date and any other requested info, confirm the transaction, and away it goes.
After the card image is securely transmitted, it's destroyed from the phone. Payment to your bank or PayPal account occurs approximately seven days later.
The app and the service are free; however, they do charge a percentage of what you charge. Currently the fee is 3.5% + 30 cents, which is on the high-end side if you're doing a lot of business, but not horribly out of line.
Links: Market (EVO) | Market (web)
[Engadget]