Does anyone know if it's possible to set something up to automatically tweet the track list whilst you're playing a set from Pioneer CDJs?

Trick question: it is. I made an app to do just that. (also scrobbles to Last.fm). https://github.com/ben-xo/cdjscrobbler

I'll admit you may need a passing knowledge of Terminal to get it up and running, and also, I'm fairly sure hardly anyone actually wants to do this - however, if you happen to have a radio show, it beats tweeting the tracks yourself!

It's free. Hope someone enjoys / finds a use for it