that one seems like a decent idea. I wouldn't call it earth shattering, but it's a good use of the touch screen.
If this is going to have connectivity, then I can think of a few ideas, but aside from that, everyone has called the DS something that will be loaded with ideas, and I see one that's not bad.
Think about it, anyone think of any way to innovate fighting games? No, you can't use the touch screen to simulate an attack,because it would take too long. And using it to target specific body parts would be almost impossible with the movements of both characters. You would need something that you can do without taking your eyes off the screen. Anything that involves jamming the touchpad, or touching it once is not going to be anything near innovative.
How about first person shooters, aside from using the screens to show two characters, or a different view of one. Once again, on two character mode, touching the screen to move between characters is not innovative, or is using the screen to move one character. That would be too much work.