Our questions have been answered, here is an article for Guitar Hero: On Tour, for the Nintendo DS. Yes its not the Wii, but its related, you know?
http://www.friendcodes.com/forums/news-and-notes/78372-guitar-hero-on-tour-heads-to.html
I'm a little dissapointed since theres only 4 buttons, theyd need to make expert pretty darn hard to keep up with the console versions. But if its got a decent number of songs, then I'd be very happy with just Guitar Hero light on the go.
Looks interesting. Thanks for posting this.