I realize the nunchuk is attached to the Wiimote, but in boxing, for instance, how does the Wii know that you've punched with the nunchuk hand? It doesn't alway seem to respond as I expect it to, but overall it does seem to know when I've punched with it. Is there some wireless sensor in it? Otherwise, I don't see how the Wii would know you've punched with it.
Or maybe something that senses a rapid movement, and it sends that to the Wiimote through the wire.