If you're picky about how your phone's case looks and feels, you can build your own tough, lightweight case at home with carbon fibre.
Cases are a great way to protect your phone (and get a great resale value), but many are bulky, don't fit well, or just don't exist for certain more obscure gadgets. With a bit of carbon fibre, a wooden mould, and a resin to pull it all together, you can make your own strong, lightweight protector for just about any gadget in your backpack. You'll need a good selection of tools, like some C-Clamps, a drill, a dremel and others, but with a well-stocked toolbox and a trip to the hardware store, it shouldn't be too difficult to do it yourself at home. Hit the link for the full how-to.