You can sort of do that now actually. It can produce an awful lot of keys and the timing isn't accurate (what is "real" time?This last one is kind of crazy, but bear with me (and if this already is a feature, let me know cuz I'll use it all the time) - what if there was some way to do animation live, runtime?

In a couple of experiments I did I hit the play button and moved bone/s around. The trick to this for me was having a simple rig setup. For instance I have a very complicated mouth rig with lots of bones, but it uses just one bone to open, close, stretch etc, the lips. I could almost do lip sync in real time by moving the mouth like a puppet while I listened to dialog on my headphones. Unfortunately I couldn't match the real time key framing to the sound file.
Another tip for this if you want to play with it, make the animation length as long as possible, otherwise it loops around and you overwrite the motion.
It can work but the program is not set up for it if you know what I mean.
-vern