I always carry my iPhone in my rear jersey pocket. No plastic bag needed since every iPhone since the iPhone 8 has been waterproof. I always have it in a case that has a lanyard attachment and I have a lanyard that goes around my neck. That way if I pull it out while moving, either to take a photo or glance at the map, there is much less worry about dropping it. Also, if I were to crash and it came out of my pocket at least it would be attached to me.