Brultech ECM-1240
The Brultech ECM-1240 is a whole home energy monitor that uses current transformers (CT's) in your home's electrical panel. Brultech provides some nice example installtions on their website. The ECM-1240 communicates back with a computer via an RS-232 port or an optional XBee wireless card to communicate on a Zigbee mesh network. You can see different Brultech communication options on their page here.