I tried this sahreware product on my MBP 2.0GHz/1GB and it works quite well. I sent the author and copy here my two suggestions for future use (also note that the prefs don't appear to work in the pre-registration version). These may already work in the registered version but I can't tell.
1. color the left and right idices of the graph to match the color coding of the two graph lines. Current in Amps is purple by default, and voltage is green.
2. Monitor MBP case temperature (I believe this data is available from the machine), either as a separate function or as a separate (future) product. The case temp varies considerably while in use. My MBP can get too hot for a lap at times. It'd be nice to know what the temp is when you have it on the desk.