Hmmm...I like the concept. When I first read the title I thought, how do you make the game. We both came up with the same solution. Use the touch screen with no video image to have to aim by judging where the character is realitive to the other screen.
Hmmm, I would think it might be cool to have a 2D overlay of the enviroment on the bottom screen. One that doesn't show the people moving just lets you have an easier understanding of how you are supposed to aim.
There is also some really cool things you do with level design with this. For one you can have the touch screen represent a flash light and the top screen is dark unless you are shining the flash light in that area. That whole design would be great for a survival horror game actually.