Developing Anti-Phishing Tool

To Create a Anti-Phishing Tool, my proposed idea is to have an extension in Firefox that reads a localized database with blacklisted URL's and prevents users from entering site, this should work with blacklisted emails too. Reverse engineering of an existing tool is allowed, I also want a step by step guide at the end on how you made the extension so that even non-computer users can understand how you developed the tool and finally carry out simple black and white box testing of the developed tool. overall the project is suppose to be simple so keep it as simplistic as possible with minimal desin.