Bookmarklets are a string of JavaScript in the form of a bookmark that gets executed when you click on it. They can be used to modify webpages or unblock things.
Tunnel is a bookmarklet that puts a link into an about:blank tab. This does not unblock it, only hide it from your search history. When you click it, it will send an alert asking for the URL. It MUST start with https:// or else it will fail :/