I have customized Brian Peek's wiimote tester application for a research project I am working with. We started with GlovePIE but wanted to migrate to something where the source code was available (thanks Brian!). I made some small modifications to the library to support up to 4 wiimotes (this was my fist stab at programming in C#). We are still tweaking the application to our needs but here is the source code for anyone to look at or use.
http://people.vanderbilt.edu/~nicholas.d.snyder/wii/WiimoteRecorderSource.zip
http://people.vanderbilt.edu/~nicholas.d.snyder/wii/WiimoteRecorderEXE.zip
Modified code for multiple wiimotes (written summer 2007 with the 1.0 version of the wiimote library. I have since graduated and this link will stop working once they revoke my webspace)