Not quite the same thing but Rbutr (http://www.rbutr.com/ http://www.rbutr.com/) was features on HN a while back. In their own words: "rbutr tells you when th

Not quite the same thing but Rbutr (http://www.rbutr.com/ http://www.rbutr.com/) was features on HN a while back. In their own words: "rbutr tells you when the webpage you are viewing has been disputed, rebutted or contradicted elsewhere on the internet."