I've seen a PC based utility that does this with an interseting approach; it uses the 2 sound card channels to track the voltage and current readings, does the math and displays all the parameters on the screen. The simple coupling hardware is also described in the help section. The company's since changed its name so it took some searching, but here it is. http://www.infinitespectra.com/freew...400/index.html

Since you can calibrate the software for your own setup, I'm sure the components arent too critical either.

And did I mention its free?!

Regards,

Anand