chrome-annotate aims to bring annotation without the overhead of a) having to rehost a site and b) relying on web authors to include special functionality. The goal is to have notes transferred over WebRTC and transparently stored in chrome.storage.sync. The end result is being able to see annotations on the original URL without content author's having to add functionality. It's a beautiful way to scale annotations to any page on the web.
This project is still very much in progress, but a demo should be available soon.