A full-stack projet that report cool URIs: https://www.w3.org/TR/cooluris/

URIs are cool up to the moment they change, so the service will register a URI and says if it is cool or not.

The service can be extended and provide a timeline when a URI was cool, when it became not cool anymore. And the less cooler it is.
Also it can provide stats on the coolest URIs registered :)

Checking a URL can result in 2 states:

• the URL is stored and the service is checking it stays cool
  • cool since YYYY-MM-DD
  • list of changes as timeline
• the URL is not stored and the service register it for the first time.