I made this wrist mount for my hero2 by hacking the original plate that was in the box. I use it for diving, but since it is adjustable, you can mount somewhere else also: tried it on my upper arm while motorcycling, and works pretty well, giving an interesting picture: records the road, while my head is in the mirror.
I didn't make photos of the steps, but I will highlight on the assembled kit each of the steps you have to follow.
Step 1: What You Will Need
Gopro plate from the original box.
Something to cut plastic: I used my swiss army knife.
File to soften the edges.
Drill to make holes in plastic. Wood drill will do, it has a pointer to help keep in position.
Electrical fast ties.
Straps, and buckle from an old backpack.
Step 2: Cut, Drill, File
Cut out from the plate the mount part. Leave ennough space to make the holes, but dont make it too big, because it is not curved, as your wristle is.
So the aim is in the final product just to have as small flat part as can.
Also cut two additional parts from the plastic plate with the same widht, and height as the mount: that will fix the strap in place, giving more stability for the mount.
File a bit the edges where you cut, not to have sharp.
Make 4 holes in the mount, and also into the two additional parts: make sure to align the two parts to the mount, and mark the holes before drilling.
Step 3: Assemble
Backpack shoulder strap is good, because it has a soft lining inside, and wide enough to fix the plate onto. You also have to use other part of backpack: some other straps with buckle on it. Make sure to have long enough wherever you want to fix it, but don't use too much of the shoulder strap, since you will not able to tighten enough.
Sew the straps together, dont forget to include the buckles aligned in a correct position. Use the backpacks shoulder strap, align the 3 parts, cut holes to strap according to holes in plastic; Put them together, and fix with the zip ties. Put the fixing part of the tie on the top, since on the bottom it will make uncomfortable on wrist. Tighten it well.
Step 4: Velcro
Additional upgrade I realized that will be needed: velcro stripes to fix the straps after tightening the buckle. I didn't make it yet, but definetely needed. The buckle looses its tightening while wearing it: it is subjected to vibration, stress, your arms movement, water flow etc..
As alternative usage you can fix it to different areas, that can be interesting for other sports, like skiing, water sliding.
Next time I will try scuba diving fix it to my leg facing backwards..
To wear it for different sports you have to consider the thickness of the clothes you are wearing, when measuring the length of the straps.
Any questions, suggestions, just let me know.