I really like the fact that you can hold multiple currency accounts in one place - I currently use 5 currencies every month while travelling for work.
It would be very useful to get a gross balance of all currency accounts held - represented in a single chosen currency. The maths to accomplish this is simple for an app that has access to the exchange rates between currencies, and while the figures can fluctuate second by second, a snapshot gross balance with a time stamp would be very useful.
Call it Gross Balance, and allow the user to select the currency.
Would anyone else find this a useful option?