In 2004 there was a skunkworks project within Danger to merge a color Gameboy with a hip top—we called it G1. The hiptop’s color screen was manufactured by Sharp and happened to be the same one used by the Gameboy Advance. There were other common components as well. So we figured that if we had virtually the same hardware as a handheld game player, why not play those games?
We extracted a Gameboy Advance chipset and built it on to the backside of the hiptop’s main board. We then developed a custom chip that would let us mix the video signals of the Gameboy and the hiptop so that on a per-pixel basis we could decide which to show on the screen. We made hiptop software that would let us start and stop the Gameboy, or play/pause a game, etc. The Gameboy inputs came from the hiptop’s d-pad and four corner buttons.
This let us do the following demo: start a Gameboy game and be watching regular Gameboy video. Then you’d receive a phone call and the Gameboy game would magically pause, and a hiptop alert window would display over top of the Gameboy video asking if you wanted to answer the call. As soon as the call was over the game would resume.