Refresh a page every x seconds and notify w/ sound or pop-up of a change?

I already have a Firefox add-in that will refresh tabs for me every x seconds/minutes and it works great. But today, there's one page that I'd like to keep a close watch on for changes so I can act quickly. I'm working w/ a little laptop monitor, so I don't have room to display two windows simultaneously.

Is there an add-in that can continuously refresh a page and then notify me audibly when the page content changes? (every 1 minute or less)  Barring the audible notification, one that would create a pop-up window? Anything to draw my attention, since I'll have my eyes elsewhere on another tab or window.