Back Again? by Jim Kang

This add-on puts a button in the toolbar that shows how many times you've visited the current site that day. If you click that button, you'll get bar graphs showing how many times you've visited the site each day that week.

I don't know where to put the privacy policy, so I'll put it here: Your data never leaves the add-on. The add-on never makes network calls. Check out the source here.