Hi,
I think this would be a GREAT app. For me, I frequently check currency rates, but I also need historical currency rates for certain records. For example, it would be useful to know not only the current conversion rates but also what the rates were for a certain date in the recent past (i.e., < 1 year ago).

For eye-candy, the ability to graph of the rates over time might also help someone like me (an ex-pat overseas) whether or not I should start transferring foreign funds into the host country or whether the exchange rate trend makes it more wise to leave funds in the home country's bank.