Over the weekend Ed Summers released a tool called diffengine that monitors an RSS feed and then posts captures of any changed text to Twitter. It's meant for monitoring news sites, but could be used for anything that has an RSS feed. Useful for monitoring your news site of choice for disappearing news, but also reports that change on the fly, here's what it looks like in action, from a CBC article:
Probably a really neat tool for journalism students too! Right now there are a handful of mainstream or influential sites publicly posted, such as The Washington Post, Breitbart and the Toronto Star. Not sure if there will be a logical directory of these things once people start running their own instances?