Mega Board
This is pretty neat, uses LEDs instead of RFID. Requires line of sight to transmit, but that’s actually a good thing…

“SecureLED is an optical access control device which replaces current RFID or Magnetic Strip technologies with a cryptographically secure, contact-less device which communicates over commodity Light Emitting Diodes (LEDs).
Project Summary

This project started with one central premise: current physical access control systems are insecure in fundamental ways. We sought a way to remedy this problem, and came accross recent work which demonstrated the potential of communicating over cheap commodity LEDs. We used these as the basis of our system, building on top of it devices which use a cryptographically secure challenge-response protocol to authenciate a user.

As such, we built both a reader and a small key device (which we had originally planned to implement on an ATTiny2313, but did not for reasons listed below). The reader outputs the industry-standard Weigand protocol, so it is interoperable with current systems. All in all, we believe that this solution presents a powerful alternative to current technology. “ [via] – Link.

Code is available on the site too.