Okay, let's clear things up.
The Wii Wheel will come packaged with Mario Kart Wii on release, but you can get one seperately for 2 player. Personally, I think it's pointless having a plastic shell in a racing game - it defeats the point of the Wii Remote's philosophy.
The Wii Zapper is out by the end of this year and it will come packaged with Nintendo's own software (game) much like Wii Sports came packaged with the Wii and the free Wii Remote with Wii Play. Games like Resident Evil: The Umbrella Chronicles, Ghost Squad and Medal Of Honor: Heroes 2 will work with the Zapper with no problems.
There.