Yeah, I considered making a Chrome extension that shows different indicator icons based on the state of isvhsopen.com. Sort of like an IFTTT Chrome extension. I’m sure it’d be easy, but it seemed like such an obvious problem (website polling + regex-based query = notification) yet I couldn’t find an existing one (or even reasonable search terms for it) so I never got around to doing it. After all, if I don’t know what to call it, how is someone else supposed to find it?
And you are correct that isvhsopen.com does not currently auto-refresh.