As far as I know, no application uses head-tracking in wii yet, except for that "demo". Moreover, the only application who plans to implement head-tracking in future versions is the Revolution Engine, and it's not an application itself. After Revolution engine implemented it (version 0.4, 0.5 or later) Someone should create a game using it, and then you would have an app with head-tracking.
However, Head tracking is actually quite simple to implement, that's not the problem, the problem is that head-tracking works for nothing if you dont have a 3D background to show, and most sceners seem to be afraid or dislake 3D programming on wii or homebrew. So again I suggest to take a look at the engine.
CJ