I'm using MPower.
Its a system set up by SRP, my electric supplier, and it does pretty much exactly what you would want. There is a small console that plugs into an outlet inside and communicates with the power meter outside through the electrical lines using X10 technology. I can cycle through prompts that show hourly/daily/monthly costs, as well as showing exactly how much power I'm using during those intervals. It has a 'credit card' slot on it, I fill a card that they supplied me with at an MPower paystation, I can put as much money(credit)on it as I want, so I pay for power as I need it. I wasnt sure how I would like it, but it definitely has its advantages. I can see the power I'm using and adjust accordingly, and there are no more monthly electric bills.