Have you ever had "waterproof" gear soak all the way through? Or drenched everything in a surprisingly deep water crossing? Or had your top case leak and hold a half gallon of standing water? WhenItPours.com waterproof sleeves will save your phone (and other electronics) from certain death in situations like these.
I kept our iPad and iPhones in these sleeves during our ten-day Goldwing Tour, packing and unpacking them a few times per day and even now, they don't show any significant wear. While we didn't get the opportunity to field test them (read: get miserably wet with soaked luggage), they kept my phone perfectly dry while it was fully submerged in a bowl for half an hour. They're the same general idea as a zip-lock freezer bag, but purpose built for keeping electronics safe and dry. The seams are much larger and stronger, the material itself is anti-static, chemical resistant, and the phone sleeves have a clear side that's touch screen compatible. $5 for phones, $8 for ereaders, and $10 for iPads.