SentinelLinks.js

// ==UserScript==
// @name      Adds a Sentinel link to answers
// @namespace https://gist.github.com/Bhargav-Rao
// @author    Bhargav
// @match     *://*.stackoverflow.com/*
// @version   0.01010
// ==/UserScript==


(function(){
  $(".post-menu").each ( function (index) {
      var thisObj = $(this)
    var postLink  = thisObj.find('a[class="short-link"]').attr("href");
      if(postLink && postLink.indexOf('a')>=0){
      thisObj.append('<span class="lsep">|</span><a href="http://sentinel.erwaysoftware.com/posts/aid/' + postLink.split("/")[2]  +'">sentinel</a>');
    }
  } );
}());

Can you please change the header to something like this:

// ==UserScript==
// @name      Sentinel Link to answers
// @description Adds a Sentinel link to answers
// @namespace https://gist.github.com/Bhargav-Rao
// @author    Bhargav Rao
// @match     *://*.stackoverflow.com/*
// @version   0.1
// ==/UserScript==

The current version can't be automatically installed/updated by Tampermonkey