What about using the Wii's Nunchuck instead of the Wiimote? I haven't tryed this hack yet but hope to soon.
Check out this link showing how to hack into the Nunchuck with a $30 Arduino microcontroller and a $20 Nunchuck.
http://www.windmeadow.com/node/42
The problem with battery power is solved, the Nunchuck gets its power from the microcontroller. I don't think the Nunchuck uses IR like the Wiimote.
BTW, I started using the Arduino and I like it as an inexpensive robot controller to play with.
Vince