The two meters, US and UK, do look like they are made by the same people:




The US one claims:

"Connect your appliances into the Kill A Watt™, and assess how efficient they are. A large LCD display counts consumption by the Kilowatt-hour just like utility companies. You can figure out your electrical expenses by the hour, day, week, month, even an entire year. Monitor the quality of your power by displaying Voltage, Line Frequency, and Power Factor."

So it looks like it will probably do everything that I want.

Edit: in case anyone is wondering what makes these devices tick, here is the inside of one http://cafeelectric.com/killawatt/

There are also instructions on its use here http://k0swi.microlnk.com/REVIEW/P3/P3%20International%20Kill%20A%20Watt%20REVIEW.htm