First off, does the electricity company's meter multiply the voltage
by the current to calculate the power, regardless of the phase?

I'm looking at whether to buy a wireless electricity monitor such as
this:

http://www.amazon.co.uk/Owl-Electris...lectricity/dp/
B000LQ79Q6/ref=sr_1_1?ie=UTF8&s=electronics&qid=1202911664&sr =1-1

which clips around the input meter lead so measuring the current and
multiplies this by a set voltage to calculte the power consumption.

Or to buy a power monitor that actually measure the power used by the
device:

http://www.amazon.co.uk/Plug-In-Powe...gy-Monitor/dp/
B000Q7PJGW/ref=pd_bxgy_ce_img_b?ie=UTF8&qid=1202911664&sr=1-1

Thanks