I know it would be awkward on some games, but some others like Metroid Prime Hunters and Mario Slam Basketball would really benefit of it. I know it's possible (at least on OSX) because Apple let's users use the trackpad to sign e-mails and there are some third-party apps that use it in a similar fashion, like Inklet, which uses the trackpad to draw. Playing NDS games can be difficult on a computer, so instead of pointing and clicking, a great alternative would be to map the trackpad to the NDS touchscreen.
