For those who uses boonie hats rather than helmets and wanting to mount a GoPro action cam, the Brain Exploder has the solution with this GoPro Boonie Hat Mount... "A much requested product is now available to anyone interested. I've had several viewers ask me to design a boonie hat mount, I gave it a bit of thought and after several variations it is now ready to go. I would recommend picking up a hat with a loose band as the video describes and maybe going a size up to allow for a little more slack and comfort.
Get 'em here: