Regardless of how much you've spent on your latest smartphone case, odds are that come World War III, there's no way it'd survive a fission-powered explosion... or even a regular explosion. That is, unless you build yourself a case like this.
Called the "PANZERHANDY" by its creator bartolo, the case was built from several metal sabots (the kind you find on furniture, not fired from a tank). However, to get the cool, almost retro sci-fi look that bartolo manages, you'll have to repeatedly grind, weld and polish until you never want to grind, weld or polish again.
While few would take the time to build their own replica of the PANZERHANDY, or even uses it as inspiration, with a little more finesse in the details, I don't see why bartolo couldn't get a manual production line going and sell the results. The next global apocalypse might not be immediately on the horizon, but you'd be red in the face if your phone was on the receiving end of a depleted-uranium round without the protection of one of these babies.
Bartolo has quite the photo gallery illustrating the creative process over at Instructables, if you're keen to take a look.