Been using this diy gopro/fpv cam holder with pan function for sometime now but thought I'd try a polarizer on the gopro. Landscape photographers use circular polarizers to cut down on reflection & enhance colours, especially greens & blues so seems logical this would be a good idea for a gopro. I have the filter mounted on a 34mm - 46mm converter that's glued to the holder. A 46mm polarizer then screws to this and also a 46mm lens cap for travelling protection. It would also be possible to use other 46mm filters. A crosspoint star filter comes to mind for low light for effects but you get the general idea.
All bought from ebay for around 10quid.
No videos done with it yet but can't see a problem, will tray over the weekend.
(http://i.onfinite.com/MgVsdSws.jpg)
(http://i.onfinite.com/z4dtdSws.jpg)
Also adds an element of protection to the gopro.
You might get some nice results with that but watch out for low light conditions because polarising filters will typically lose about two f stops.
Haven't had a chance to test as it won't stop blowing down here on the essex coast. Nice & sunny for a while but always windy!