Or you can redirect the links to an article where say something like 'You will visit other page...'
+ Added option: only registered users can look external links
In my web and local the plugin works in front page. I use 'onPrepareContent()', so it changes all articles loaded.
Maybe you use a plugin that is not compatible with this plugin.
If you want, you can post a message in my forum (http://www.jonijnm.es/web/foro/765-plugins.html) and we will try to find what's the problem and fix it
Suggestion: the support forum is in spanish language, eventually if you have trouble to reach the right section inside the forum, try to post a comment following the Demo link.
This plugin can be the one. Right now it doesn't do what I am looking for but I am pretty sure, someone can take this idea and make it work the way I want it.