Add Keyword & Notify Post Titles

There are alot of "subscribe" plugins for wordpress, but I need a specific one. Using the same technology that notiFinder and HeyCraig and all the other craigslist subject notifiers use... I need a simple search tool that will save subscribers keywords they add and notify them via email when that keyword is posted in the ad(post) title. I've been trying to develop this as a plugin on my own, but I give up. I'll leave it to the pros. Thank you and contact me for any further info regaurding this project.