[37C3] There oughta be a Game Boy capture cartridge.

I present to you: The GB Interceptor. It is an adapter that goes between an unmodified Game Boy and the cartridge and offers a video stream of the game via USB. Click the image to see the video on youtube.com. The video above should give you a good overview of what it does, how it works and what its limitations are. This article here goes more into the technical details of how it works. If you are interested in how to order and build your own GB Interceptor, check out github and the order and build video.