Is this the type of thing you are considering:-
http://www.ecohamster.co.uk/product_info.php?p roducts_id=8976&osCsid=9m9okp87oh5gg6ss9ev2cbm ne1
I have something similar, it will display the power being drawn from whatever is plugged in to it, together with kWh and the cost of electricity used (but you have to input the cost of electricity per kWh).
If you are serious about monitoring your electrical energy usage, you might like to consider something like this:-
http://www.ecohamster.co.uk/product_info.php?p roducts_id=8975
It is similar in operation, but monitors the total household electrical usage, with a wireless display. No tools are required to install the device, it has a current sensor which is clipped over the incoming mains cable.
These devices will only monitor your energy usage, you have to reduce your energy usage to make a saving � these devices will help you measure any savings.