Occasionally when I'm feeling appropriately inspired I'll get an idea in my head for an invention. This is a bit of a family tradition as we often would come up with ideas on how to solve particular problems around the dinner table. Such an idea occurred on the way to Paul's party (much to Andy and the Cab drivers amusement).
We are always being told we should reduce energy consumption but its very hard to know exactly how much power we are using on a day to day basis. Most electrical devices nowadays come with an energy rating but this still isn't instructive when it comes to the saving you can make by for example not keeping your TV on standby.
So whats the solution? Well I envisage a adapter plug that goes between the socket and the appliance plug. It would contain a simple current meter and timer to measure the energy consumption of the device it was plugged into. It should be as simple as possible to operate so by default it should reset the counters when it is plugged into a wall socket and then when unplugged it can display the average energy consumption in kW-h and possible an energy rating on an LCD panel.
Enhancements have since been suggested to me including monitoring the voltage or noise on the line to detect when heavy loads turn on and off in the system. However the core idea of this is it should be cheap. It should be cheap enough that every household could afford to have one and conduct the "how much money do we save if we don't leave the TV on standby for a week" experiment.