Thought I might as well post these here since they're somewhat to the game.
First, 1up's review of the Zapper + Link's Crossbow Training game:
http://www.1up.com/do/reviewPage?cId=3164658
In summary, the 'official' Zapper is queer-feeling piece of plastic with a squishy trigger, But the game itself is pretty fun for the $20.
Second, Nyko's upcoming alternative, the "Perfect Shot". Which already looks leaps and bounds over the Zapper, if nothing due to the sole fact that this actually looks like a gun.