If you look on the wildstang site, I think it was under the Invention award or something they showed the circuit they used to create the current sensor and send it to a color palm pilot. Very slick, also fairly complex, if they didn't have a custom circuit board it probably was a lot of breaboarding to make the circuit in the schematic.
See here:
http://www2.wildstang.com/2002/inventor/schematics.asp
Very nice job Wildstang!