Campfire-audio-notification is a project mainly written in JavaScript, it's free.
A user script that enables audio notifications in Campfire when a message is received from a specific user or when it contains a specific word
Play an audio notification when a message in Campfire is received from a specific user or when it contains a specific word.
See http://userscripts.org/scripts/show/99950 for more details and installation instructions.
Thanks to Tim Harper and his great Growl Notifications plugin, from which this plugin is based.