So, with the matrix running I started to go beyond the demo sketch of the WS2801 library and try to make one individual pixel light up at the movement of the nunchuck controller.
Thanks to the WiiChuck Demo from thingm.com the Nunchuck was hooked up in no time. I control the position of the lit pixel with then Nunchuck's accelerometer. It looks as this might be a nice method to control the paddle in a game like Pong or Breakout or the tank in Space Invaders or just to position the cursor in Concentration (a.k.a. "Memory" ).
Note to self: the input would ideally need some kind of LPF but reducing the sampling rate of the input might suffice for what I am up to.