Let me start out with what I am trying to do. I want to always monitor this Twitter feed https://twitter.com/DuvalMagic, but when the string of “WinPC” is in a post, I want to create an email script to notify me immediately. I can pull the feed no problem, and write the email no problem, but how can i filter based on that string?
I would check the page content (code) with a preg_match() function to check if matches with your keyword. And if it does send yourself an e-mail with mail() function. Also think of something that stores your already sended matches… So you don’t get the same e-mail over and over again…
You can find more specific descriptions about these commands on google since I have no time to make a script for you 
Have to go, good luck ;D