The name "Game Boy Advance Touch" sounds a heck of a lot neater than what it really is in execution: cramming an iPhone into a hollowed-out GBA. On the plus side, it offers good protection against would-be thieves, assuming people don't go around jacking Game Boys from one another in the year 2010.
As you can see from the quick video demonstration of this project, you're still using the iPhone's touch controls to play games. To be fair, that was likely the intent all along. Looking over this post by creator Goteking, you immediately get that impression. He's wearing the thing as a necklace, for God's sake!
Give me a call when you somehow manage to get the GBA's controls to interact in a useful way, modders.
Game Boy Advance Touch by Goteking [Tiny Cartridge]