Add a picker for common loans on the market. This will allow user to pick his fairly quickly instead of having to enter all (4) settings.
Maybe I can help with this one. I like your project, you kinda beat me to it, :)
In any case, I have aggregated most of the loan choices here: http://nilsson.is/ice-mortgage/. Currently it's only in html format on github but I mean to change it into a more computer-consumable format, preferably with the history.
Awesome! I'll add these in when I get a chance.