elseif ( ! preg_match( '|^\S+://\S+\.\S+.+$|', $options['redirect_url'] ) )
That is far from sufficient as a URL regex. Consider, for example, the URL
http://localhost/~squelch which is perfectly valid. As a developer I need to test things before they go live.
It's a shame as this looks like it could be a good solution. If/when this gets fixed I'll be more than happy to revise my rating.