Dean: thanks for the encouragement!
ficusd: That's a nice link, thanks :) I also referred this really handy post about ZF from CLI, and used that for my workers: http://webfractor.wordpress.com/2008/08/14/using-zend-framework-from-the-command-line/
Mike: thanks for the pointers! I have ended up not unit testing so far, but I will take your advice when I do.
Rob: I got the same advice from weierophinney and I am indeed using supervisord. I haven't checked any of the gearman settings though, so thanks for mentioning that!