It would scan your shareable pages and ensure that all of the opengraph/schema.org tags are present, meta tag images the correct sizes for different screens and that everything is up to date with the changing resolutions/standards. It would continuously monitor your pages so that if standards change or say a software update nixed the og tags you would know immediately. I'd also try to provide accurate previews of what the posts would look like on different screens given your sites meta info. I'd have it set up so that you could test a site behind http basic auth etc, so you could test your social tags before going live with the site. (this has been a particular annoyance to me at least)
Similar to http://smo.knowem.com/ but a bit more fully featured and with continuous testing features.
Is this a service you would use? I was thinking of a 19/49/99 pricing structure depending on 1/3/5+ users and the number of pages it'd test.