It would be very nice to be able to route the sound via jack audio directly. As a musician I would would like to webcast rehearsals and recordings and would be great to just send the jack audio output directly to webcastsudio.
It would also allow people to use compressors / limiters, reverb, echo and no end of effects to "tweak" there audio stream.
I guess what you have provided for video jack plug ins could do the same for the audio.
Webcamstudio could also be a wonderful one on one tool to teach musicians how to use these effects as you can see the desktop as well as the instrument being played from more then one angle ( ie multi cam) .......