Cool project! I also use a browser extension for this currently, but the obvious advantage to this is you can use it on any browser immediately as long as you remember the domain name.

One suggestion - it would be a bit more useful if you hid the top bar while it's in "refreshing mode", and made the iframe take up the whole page. You could put a little icon in one of the top corners to reveal it again. I've used tools like this in the past to show analytics and news dashboards, and you typically want to keep as much screen real estate as possible.