For now this is just a proof of concept and but with some time invested this could be good.
My idea is to create a iOS app similar to TouchOSC that communicates using sound. Like a 56k dial up modem. It would be built with the arduino in mind. The arduino would just need a library to interpret the audio into usable data.
The picture is proof of concept all I did was connect a 1/8 inch headphone jack to a three pin headers. Then with my trusty breadboard I connected the 1/8th ground to arduino ground and one audio channel to analog0. Then I just played some notes on my ocarina app and watched the digital waves over the serial readout.
If anyone has a Mac and some experience making apps and would like to collaborate or even take the project over let me know.