Smart meters are an increasingly popular method for tracking one's electricity consumption. By having detailed information about one's energy use, it's much easier to make decisions about how to cut down on power-hungry electronics or to learn when it's cheaper to run certain appliances.
Similarly, the Kill A Watt Power Strip empowers the user with information. In its construction, it's really not that green -- it's made with plastic, like most power strips -- but by providing real-time statistics about the devices plugged in the strip, you'll be able to do even more to cut down on energy use.
Say you suspect an old appliance isn't working properly or is sucking up a lot of energy. Plug it into the strip -- which also provides information about line frequency and current leakage and protects against surges -- to find out. The strip can also estimate costs for running devices by the day, week or year.