I have built what I consider to be the ultimate climbing phone case. I designed and cut the aluminum and bartered with a buddy for the welding. Ideally it would be made from carbon fiber...but metal is easier to work with. It was noisy to carry (banged like a cowbell) so my latest trick is to wrap it in a bike inner tube for sound deadening. I can clip it to a big locker for leading, and it is secure, just like a Grigri closure. For active shooting, I clip the binier to the outside cord and pull the phone in and out with it's lanyard. The lanyard is here.
This case is so strong you could probly' use it like a big bro. I clip it to my harness or my rack sling when leading. I just carried it all over the City of Rocks for two weeks, including up a 10+ offwidth and got many shots I would never have gotten with my big DSLR. If it rains, I can carry the case upside down, it's quite waterproof.
It's not for sale, took a day and a half to make, and I had to trade a painting to my buddy for the welding work. But it works very nicely.
All of my friends just carry them in their pockets. But I don't have phone insurance, and my fingers are old and arthitic, and I'm clumsy. It was fun to find a solution that solves all these problems. Someone should print one of these in a 3d plastic printer.
Why a hard material? Rather a neoprene "sleeve" with grommet holes big enough for bieners. Lighter, fits all phones. and would probably protect better than aluminum or carbon fiber. I'd rather not have any cowbells, reminds me of racking hexes. Like this