Well I havent posted here for a while, but I do have many updates for a couple different projects. I never ended up getting full kalman filtering to work between the wm+, nunchuck, and arduino, but there have been a few other, maybe better things. First, my transistor method is no longer needed to interface the wm+ and the nunchuck at the same time. Pass thru mode has been discovered and is described (krulkip) in this post: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1248889032/45 . Second, the kalman method has been mostly abandoned on the arduino platform, and in its place two options have surfaced.
1. Complimentary filtering as seen here .
2. Direction Cosine Matrix. Not implemented with wii peripherals but easily enough ported. Tons of information over at diydrones.com . Much less computationally intense and more suited to a microcontroller like the arduino.
Good luck on all your projects!