Pretty simple idea: take the Carnivore library for Processing and make sounds based on the data it provides in real-time. Technically it tracks network packets and generates tones based on port numbers. Undoubtedly done before, but still neat. Uses the Ess sound library to produce dynamic tones.

Requires Ess r2 library, Carnivore for Processing (and for Windows users, WinPcap), and Processing 0135.

I can't make the project an applet, but you can totally download the code and try it out.