My smartphone is waterproof - but forget about working the touchscreen when it's wet. Doesn't work, at least not with my fingers.

I actually think one of those (semi-)waterproof smartphone pouches where you can use the touchscreen through some kind of transparent (plastic?) material would work much better in precipitation, at least when it's not too cold outside. Those pouches might get very stiff when it gets cold (untested by me).

And don't forget -- when it's bad I want to use the unit with thick gloves or mittens. Then I want big fat buttons to push!