Here’s a quick prototype from [Travis Goodspeed]. It’s a smart card built around an MSP430 microcontroller. We’ve used the MSP430 in the past because of its low power demands. He says this business card currently supports 1.8V to 3.3V, but a future design will have 5V as well. Technologies like Java Card exist for running applets on smart cards, but a familiar microcontroller like the MSP430 could certainly make development much faster. Knowing [Travis], there’s a reader somewhere about to go through some serious fuzzing.