@tvler I've often dreamed of something a bit similar that would discover microformats like h-card, h-event, as well as document alternates that happen to be stuff like ics, vcard, and offer to “add event to calendar" etc, so sites can more easily offer data in to PIM apps and the likes. Do you know, can a Web Extension sniff HTTP “Link:” headers for stuff like that? I feel sure it could work with in-document <link>, <a>, and microformats markup right?
@phx sounds possible!