Simulated theremin controller, ftw.
Rock Band is one of my favorite games of the last five years. It's great, and it has a decent difficulty curve. Prior to RB, I completely failed at every rhythm game known to man, but starting with Easy bass, and moving up, I now can play all the Medium songs, and a few on Hard.
Buy it. You'll be happy, but your wife will be happier. Which, um, is some kind of virtuous cycle.