I think he was referring to the hacks page somewhere on the net. I just recently ran across it as well. It used a switch to replace one of the blanks where the switch would toggle through the OBC displays if you didn't have the factory option and the LED was set to light when the spoiler was up... Pretty cool hack but it was fairly involved.
Ahh, here's what I remember
OBC hack
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http://www.whiteson.org/boxster/mods/obc/
spoiler/OBC hack
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http://wa4ekg.home.att.net/996images5/FWLswmod2.html