It's funny that you say that, because you can buy an iPad-controlled quadrotor on Apple's store right here:
http://store.apple.com/us/product/H1991ZM/A?fnode=MTY1NDA3NA...
http://store.apple.com/us/product/H1991ZM/A?fnode=MTY1NDA3NA...
From these videos it looks plausible. The hard part now would be setting up the camera to see what's happening on the screen when the copter is on top of it.
Also, the hard part of any such project is the control code.