One thing I'd find this useful for would be when you're waiting for something to be released - point this at an author's website (or a subpage related to a book you're looking forward to) to be automatically notified when the page changes. Similarly, I think that Overdrive (e-book and audiobook lending through public libraries) has a page where it lists the libraries carrying a given book. If you're hoping that your library starts carrying a given book, you could imagine following a page like that.
Another feature suggestion - maybe put in an option for a reminder to check back even if the page hasn't changed either on some interval or after some period of time. I could see using that as a tool to try to keep kickstarters and the like honest ("You said there'd be an update after 14 days, it's been 18 days, no update...").