Create Firefox Addon

Hi, I would like a firefox addon which connects to a mysql database. When you go on a website for example [login to view URL] it wants to check the database for the word 'apple' so if in the database it had 'apple computing' or something that would count as a find. It would then want to display a pop up in the right hand corner saying it has a match. Exact details will be given if you are chosen. Thanks a lot. Matt.