ioBridge, the biomedical engineering scholar measures the main electrical lines entering his house and sends the data to a Google charts widget on his personal blog that reports the kilowatt-hour usage in real time. As a footnote, he presents an example graph of when the hot water is turned on, which then produces close to 4500 watts. That's just over the amount of power he used this morning for about 1100 seconds. Of course, we can't say for certain any of these morning events really transpired, but then again, we don't exactly want to know. Hit up the read links for directions on DIYing this.