It's written in Python and runs on Google Appengine. http://firetweets.appspot.com/
It's tracking a dozen of topics — for which I'd like to keep up with what’s new. Other topics (ruby, python, appengine…) are coming soon, but the amount of spam or assimilated spam for these topics on Twitter is significantly higher than for the current ones. I'm working on a solution to reduce noise, and duplicates, but in the mean time, if this micro-service is useful for somebody, that'd make my day.
Feedback and suggestions are welcome.