If you've seen
http://bazaar.launchpad.net/~kovid/c.../feeds/news.py
there's not much more I can tell you. Basically, you can completely customize the news download process by overring the methods of that class. So if you want to create a compsite recipe you would create a parse_index method that will list all the current articles in your various news sources. Then you would override postprocess_html to check for the required keywords and if absent return None