I'm not sure if mobile phone / tablet mics are sensitive to this sort of thing, but it might be kind of awesome if, while your app is playing a test sweep, it could listen to the result and graph perceived frequency response at the same time. Even if it worked poorly, it might at least be fun to play with. As-is, the lite app is just a glorified sound board with some nags to upgrade to pro for more sound board-ish things as far as I can see.
