An interesting device I say on one of the BBC's "Its Not Easy Being Green" program was an electricity usage monitor. Seems to clip onto your meter and connects via wireless to a monitor that you have in the house.
http://www.reuk.co.uk/Electrisave-Wireless-Electricity-Monitor.htm
Could be an interesting purchase and it shows the cost of the electricity you are using.
These are available here too: [broken link removed]
Though you can pick them up on e-bay too for about €100 delivered.