It seems to me that the least vulnerable part of your iPhone 5 is the rear panel: The glass windows at the top and the bottom are tucked away, and the rest is aluminum, which might scratch or dent but it will never shatter (unless you freeze it in nitrogen first).
But if you think covering the tough rear panel with a thick plywood coating is a good idea, then the SkateBack might be just what you’re looking for. It’s a candy-colored cover refashioned from old skateboard decks.
The SkateBack is 1/16th inch thick (or 0.0625mm if you prefer a more appropriate unit), and it made from sticking together offcuts from the pile behind a skateboard factory. Once compressed and cut to shape, the backs are machined and have a sticky, removable 3M panel applied.
It looks amazing, and comes not just in the bright candy-stripe color scheme seen here, but also in more sober tones.
I’m tempted to buy one and pair it with a couple strips of grip tape up the sides of the iPhone. Not only would this render it non-slip, but would also be handy for keeping my fingernails neatly filed.