The keywords to search under are "rss" and "feed." This is a format intended for computers to read and learn about updates to a website. There are feeds for main and discussion. I don't know any particular tools, but there are certainly ways of turning an rss update into an email or a text message. There are probably apps for your phone that make an alert when they notice something new in the feed, too. The inbox has a feed, too, but that link only works if you are logged in, which may be difficult to do in the feed reader.