It is a custom made Active check.
On every of our customers website we place a Script which outputs infos about the page.
On checkmk we add the host where this result is parsed and generate some services out of it.
This is the output generated by the webpage which results in the check result I posted in my last comment.
In the moment we monitor about 200 Websites in this way. Drupal 7/8, Magento 1/2, Wordpress and Typo3.
We see at a glance which page needs CMS oder Plugin Updates, if a Meta/OG-Tag is missing, if the HDD Quota is going to be full or if SSL Certificates run out soon or if SPF Entries are missing and E-Mails a maybe not delivered correctly.