Not to be argumentative, but I think we want the OPPOSITE of a hydrophobic coating on the rear camera...
Hydrophobic coatings work on a windshield where wind speed can clear the water off the windshield
In the rear camera, it will stay cleaner MUCH longer with a hydrophilic coating so the water can sheet off rather than bead up and cause the optical distortion through the lens..
Side mirrors too, like in this YouTube, are better treated with the opposite of hydrophobic
Any Anti fog treatment will be hydrophilic... Allows water to sheet, like jet dry from a dishwasher.