When you post on facebook and other social media, and you are shown a preview of the site including it's title and an image, aren't you curious which server is going around fetching those previews? no? never? ummm...here you go anyway.
Deploy this app to heroku and post the url of the app to any site that tries to preview it. As a result of the Observer effect, the server ends up revealing it's ip address in the preview title.
Something I made on a whim