Hi Taylor,
Your work on improviser is really interesting! I do not know whether this is what you are looking for or not but, a few months ago, there was a short discussion about BPM estimation for live audio in this thread (BPM estimation from onset or onsetfeatures).
For my setting focussing on live piano, I use the Tempogram approach (based on the FFT of the novelty curve). I have improved a little bit the analysis compared to what was posted in the thread. So, if you are interested in the updated version, please let me know.