Alert for when page changes

Summary

We need to trigger some alert when we update a page

Content

We have an announcements page that is not an answer. We are wanting to show a red dot in the header to show that the page has been updated recently. Is their a way to attach a widget to the page to do this or something like this? The page is already heavily customized and we prefer not to make this page an answer. 

I am willing to look into anything. I am going to look at the answer alert widget and see if that bears any fruit. Any advice would be much appreciated.