Detecting the BPM of the audio signal is not an easy task, and nowadays, when DJ's and Producer's are working with smart hardware mixers like the Pioneer DJM 800 - which has a great hardware tempo detector and a midi out, so we can use it as a midi clock source in applications - or the more recent software solution Ableton Live - which is also midi-syncable - BPM detecting of the live audio is not the recent thing we want.
But it's still a funny and interesting territory, so last time i had a question about how-to-detecting-bpm-and-sync-to-CoGe, i've just did a very quick research, and found a promising application BeatDetektor. Its open-source and i made a quick port of it to make it work as a Quartz Composer plugin, and the result just called CoGeBeatDetektor.
Its not the smartest plugin you ever seen, but just do the job: detects the BPM of the incoming audio signal, using system-wide default audio input device. The result is really good and there are some situations where it can be very helpful.
The downloadable archive is also contains an example composition to send the detected BPM value to CoGe via OSC. So, download and install it, and have fun with it!