Has anyone interfaced an Arduino to the "WATTS UP" wattsupmeters.com
Serial - looks straightfoward.......famous last words 
is the serial port on the new ones or the old ones?
https://www.wattsupmeters.com/secure/products.php?pn=20&wai=0&spec=2
I just see this unit, which has ethernet and usb.
The Pro has serial over USB
Is it anything like a Kill A Watt...
http://www.ladyada.net/make/tweetawatt/