This is Geode. It’s an iPhone 4 and iPhone 4S case by iCache. It’s designed to act as multiple credit cards, keeping you from having to carry around several pieces of plastic.
The case doesn’t work like NFC payments, rather it uses a rewritable card. Your information is registered with Geode, and you can use the magnetic strip just as you would with a real card, to make purchases. The most useful part is that you can use the app to quickly change which credit card you are using. This makes it particularly useful and almost serves as a wallet replacement.
We’d definitely like to take this baby for a test-drive. It’s not available yet, but they are taking orders.