I posted this elsewhere but figured this might be a better place to have it.
I've seen a few requests for voice to air and voice tracking, obviously an in studio option is line in via a sound card but remote audio could possibly be done using speex (http://www.speex.org/). Our conference bridge at my day job uses speex with virtually no latency.
I'm not a software developer by any means so take this with a grain of salt, just putting the idea out there.