While I’m thinking about it I would like to write the following.
AccumulatedCraigslist ~ give it the subject,. say Celica, and a radius of a zip code, 30,60,90,120,300 and have it setup an hourly cron job to pull down listings.
If it finds new listings it emails to notify you, then you can mark them in the system as hot or not.
RSS Reader, Zip to Craigslist Feature, Cron script running hourly to look for new filters from mySql data; parse searches, etc…