Problem Statement:

Pull realtime tweets from Twitter that match certain hashtags, queue them in MongoDB, and process them into a specified data format, saving the image.

Use Phirehose PHP script, running as a daemon?

php upstart daemon: http://kvz.io/blog/2009/12/15/run-nodejs-as-a-service-on-ubuntu-karmic/ (http://kvz.io/blog/2009/01/09/create-daemons-in-php/?)