I want to be able to change the audio input (what was the microphone by default), and to change it to what would normally be outputted to the speakers.
My ultimate goal is to be able to, when talking to someone on the phone (either the phone stock app or a third party app like Skype), change the input from the microphone to a simple audio file. So instead of hear my voice from the microphone, the person on the other end of the call would hear an audio file instead.