this is possbile, audacity has the option to create the 'oppsite' of a sound file. it's open source too? i wish I had programming knowledge of some description, but i'm a musician so I don't :P all that needs to happen is for the n900"s microphone recorded 'input' to be reversed and played back through the output. this wouldn't work for calls but for music listening it'd be sweet. i think i'm right. or maybe i'm completely wrong, whatever the case it'd be a sweet feature to implement!