It's pretty simple; each time the browser loads a website that has potentially distracting content (think: twitter, FB, reddit, hacker news, rotoworld, etc) that I tend to over-visit in search of new tidbits, the extension keeps track of my visit and the text content of the page.
The next time I visit, I do a text comparison that checks how similar the content is to my last visit. If there's too much overlap, the browser redirects.
There's a profound difference in using this approach versus existing distraction-detractors. When I see the browser redirect away while trying to load reddit.com, my rational side takes over and reminds me that I should be done with tidbit-seeking.
I ought to clean it up and put it on github; I'm sure someone else might find it useful.