Iphone waterproof & Manual Tools 7 in 1

Waterproof phone cases are a dime a dozen, but it's hard to find affordable versions that are any good.
Taking a fragile device worth several hundred dollars underwater is nerve-wracking, so you need a case that works exactly as advertised – but for most people, it's something that happens a few times a year at best, so they don't want to spend hundreds of dollars to do it.
At $4, the Waterproof Case for iPhone 5 / 5S is cheaper than many of its competitors – but is it any good?