This handy device monitors the amount of electricity a house is using and displays the information in real-time through its LED display. You can see, for example, the kilo-watt hours being used, or the calculated cost per day. It also projects the next electric bill, based upon local rates.
The monitor itself sells for $200, which could actually buy you quite a bit of electricity. It is mostly recommended for those who want to “sub-meter”. Another device, the “Kill-A-Watt” does the same thing but monitors single appliances. More information: Whole House Energy Monitor