I am not sure if that component will help you either.

What you need is a script at your site, that will accept the URLs in "nice" format and then redirect them to the external URL. (which I am not sure the ReReplacer can do - it may replace the external link with the nice one, but it will not do the needed redirection)

I am afraid that is not easily possible.
A special extension would be needed that could take care about rewriting outgoing URLs and then taking care for redirection.

By default, JoomSEF will only rewrite "local" site links starting with "index.php...".