The funding campaign for Impervious is in the home stretch of offering affordable, easy-to-apply waterproofing and scratch protection for your iPhone. Users simply spray on and let dry. Apparently there's no residue left behind at all, assuming you follow the instructions. Each treatment is good for three years, though it uses up the whole $30 bottle.
Your iPhone's camera and speaker system are unaffected by the treatment as well. Though a complete internal and external application should provide submersion protection, the developers aren't suggesting it. In any case, an external application will protect against spills of all kinds.
The only viable consumer-grade aftermarket device waterproofing we've seen is from Liquipel, and they need you do ship in your device. Though it might feel a little sketchy doing this process on your own, and there's no way to know exactly how well Impervious works until you've bought it, applied it, and personally dunked it in a glass of water, the demo videos show treated iPhones working after a splash without a hitch. As with any waterproofing device or Kickstarter campaign, there's a little leap of faith to make before getting involved. Are you in? Hit up the Impervious Kickstarter page to get started.