HTTP Redirect
From DD-WRT Wiki
This feature has had some changes made along the line. In v23 SP1, there is now a setting for destination port and also a setting for "HTTP Source Network".
HotSpot HTTP Redirect (v23b2+)
Option found in Administration/HotSpot/HTTP Redirect
This option enables an HTTP redirector for proxy usage.
The amount of information currently provided is minimal; please update this section with more information.
I'm not sure exactly how the DD-WRT interface works, but you can read about how NoCat works at http://nocat.net.