I would love to have the ability to display and/or grab a category balance for the current month and then display on a phone. Basically, my wife could care less about looking at a budgeting program, however she would look at a widget on her phone listing the balance of our monthly spending category. Just a thought ;)
If she is running on Android I would think this could be possible with (the amazing) Tasker app; though I doubt its simple.
Unfortunately, cateogry balances are calculated client-side.
So it's totally doable (just need to know a bit about CouchDB), but it might be a bit of work to extrapolate the balance from the transactions, budget amounts, etc. :)