Send e-mail notifications if people post topics with certain keywords. Add a UI for adding words to watch. They should probably not be in the search stop list, it could be possible to use the word table for this, seeing at it checks each word when posting for the search function.
The post you reference in the URL is gone; what do you need this for?
The thread is visible if you are in the developers group on the forums. It's a feature request for the forums for a notification mechanism/RSS feed which you can filter by keyword.