We received a contact request on Plone.com from SiteImprove.com. They inquired about having an integration with Plone, similar to the ones already at https://siteimprove.com/product/cms-plugin/
I had a hangout yesterday with their sales contact and their sales engineer.
It seems like a good idea to me, and certainly I am interested in having something similar in Castle CMS (we have accessibility compliance checking in Castle's content quality check feature and Google Analytics reporting on each page, if you have it enabled) since SiteImprove combines those features plus spell checking, broken links, and a bazillion other things).
This is an FYI, in case anyone is interested in picking it up or helping to make it happen...