If I end up putting one together I want that sort of functionality on it as well, with all the historical records. Also thinking the deviation of each of the exchanges during that time period would be a neat feature (i.e., Gox is 5% above average, Bitstamp is 3% below, etc.) And the changing percentage of each exchange over time. Just need some time to work on it...
Nice!
I'm looking for a weekly average so I can use it in contracts which I expect to be paid within the following week. I don't want to use the latest value because BTC can change too much day-to-day.