I recently purchased a GoPro Hero3 Black Edition, mainly for recording my auto sports. It came with a full acrylic case as well as a "skeleton" case, to allow more sound to get to the internal microphones.
I shot some video and the sound was dismal. It was muffled and had bad windnoise. No-go.
I bought an Olympus ME-51S stereo mic, and the short adapter cable for the GoPro. I also had to buy the "super skeleton" acrylic case that allowed for the cable connection.
I wasn't fond of using the 3' extension for the mic, and there was no good way to secure the mic without it. I wanted to be able to have everything secured to the camera, plug 'n' play.
I modified the straight cable into a loop, used a Dremel to notch the connectors, then epoxied the connectors together to form a solid, single piece for my mic attachment. It worked great, and when I added some homemade wind screens to the mics, most windnoise is gone. Success!
Ignore the crude windscreens. This was a prototype, and will be replaced with real windscreens.
Here is the video I shot with my modded mic setup. Listen to the video through a high-quality headphones, or a good sound system. It sounds like you are standing behind the car, in stereo! The camera is suction-cup mounted to my Camaro on the bumper.
Enjoy.