You can go insane deciding on methods to mount your GoPro. Everyone has their own special devices, but GoPro wants you to buy their own. The latest is the 3-Way, which has a few functions in one, and is definitely not meant as sexual innuendo.
The 3-Way's primary use is as a simple extension arm. There are plenty of those out there, but this one is flexy and bendy for some added versatility. It also has a 3-legged attachment for when you want to set up a stationary shot. Pretty handy. The third function is simply using the 3-Way as a "grip," which is kind of not a function at all, but hey, the "2-Way" just doesn't have the same ring to it.
The device costs $70, which seems steep, but if it is well-built, easy to use, and portable, it might be worth it. [GoPro]