Such a thing would have been very helpful to me. My domain's SSL cert expired and I got a new one but didn't notice that my provider had shipped a different, newer intermediate certificate.
For three weeks I was showing a great big THIS CONNECTION IS UNTRUSTED screen to Firefox users and didn't know it.
It surprises me how common it is, which made me build Domainsquire to fix it. As today's event shows it even happens to the big boys, and this is a predictable, pre-emptively solvable downtime event, so it really shouldn't happen.
For three weeks I was showing a great big THIS CONNECTION IS UNTRUSTED screen to Firefox users and didn't know it.