This weekend was the first 57N Stupid Shit No One Needs Hackathon. I tried this weekend to perform serial comms over a string and cup using the msp430 based TI Launchpad.
I had the tone generation working really quickly and then spent 15 hours trying to demod and tones and find a byte stream using a microphone. I had no chance, it didn't work at all.
I was able to transmit the tone a long the string over 3 meters of room. So the core idea does work. I think I will try this project again after reading some more dsp.