Design firm AWARE built this neat clock concept that plots your energy usage over the course of the day. The qualitative radial display allows one to quickly see what times you use the most energy. They don't appear to have released a product, however it seems like it would be pretty easy to put together using the Tweet-a-Watt and an extra computer.
http://technabob.com/blog/2009/09/12/en ... are-clock/
