http://www.smart-watt.com/

Smart-Watt keeps a cumulative total of the energy consumed in 0.1 watt-hour increments and retains that reading even in the event of a power failure.  Smart-Watt conforms to ANSI Standards for watt-hour meters so you are assured of the same high accuracy standards that public utilities require for their meters.  Smart-Watt is a "1-Wire" compatible device utilizing a Dallas/Maxim DS2423 to keep track of cumulative energy usage.  Twin RJ11 connectors with standard 1-Wire pin outs provide connectivity and make it easy to daisy-chain multiple Smart-Watts together with other 1-Wire devices.