Does your electricity meter have a flashing LED on it?
This LED is actually telling you the exact instantaneous power consumption of your household. With the LED Power Meter app point your iPhone camera at the LED and it will read this exact power consumption in kilowatts.
Typical "clamp meter" electricity monitors become very inaccurate at low power levels, this makes it hard to reduce your "vampire" standby power or see what improvements you make from changing appliance settings or fitting efficient lighting, LED Power Meter solves this problem.