Y3LLoWF3LLoW: Wax isn't really gonna help your phone. Cars take punishment from rain and grime in the air. Your phone is gonna be taking beats from the inside of your pockets or pouches. Much heavier stuff.
i use meguiars gold class on the countertop at my parents restaurant to give it that extra shine before inspections. so yeah use it on any surface that is clearcoated or has a shiny plastic (i.e. cell phone faceplate) finish. shit i waxed our marble stairs too just to see how they'd look, dont do that tho, you fall a lot.