I have a daft 'tough' phone and have struggled to find a holder for it to mount on the handle bars of my GS. Not only is it quite thick (around 16mm) it also has all its buttons on the side so the usual RAM 'sprung fingers' mount type holders interfere with these. Most of the rest of the holders available look like they would fail in tough conditions.
Anyway, I found exactly what I wanted in the Mob Armor Switch Marball holder, right after they stopped making them. Ho hum, back to Google.
Mob Armor: NLA
Eventually I found a holder that I thought would do the trick, basically it's a Taiwanese ripoff of the American Mob Armor one, which holds my phone top and corners, while mounting on my preferred RAM system. Better yet, it was about a third of the price of the Mob Armor one. I already had a spare composite RAM arm, so I ordered up a ball that mounts in place of one of the handlebar clamp bolts. I don't really like clamps around the handlebars, they never seem quite right, and I need something that will stand up to serious vibrations over hundreds of kilometers. I did have to tweak the holder a little, and the adjusting bolt needed grinding down to accommodate the thickness of my phone as I removed the small foam pieces, but once that was done the whole shebang seems very steady, and I don't think there is any danger of the phone being lost. I can still plug the phone in to a power source too if I need to.
Daft (but waterproof) phone with buttons in the wrong place.
The holder. I removed the foam pads on the plate bit, a thinner phone would not require this and so you would not need to grind down the adjuster bolt.
Phone in holder. I decided I needed this facility after a problem with my GPS's mount - the power connections failed on the last trip. Also, it's handy having another map (Tracks for Africa was a bit sketchy in some cities for example, so Google or maps.me is handy) and of course being able to control my music without having to dig the phone out of the tank bag is useful.
Without the phone
Showing the RAM arm. The holder comes with its own 1" ball which seems to be reasonable quality.
I would say the finish is a little iffy, but that's not a massive concern. I can still see all the idiot lights and speedo sitting on the bike as the arm allows the unit to be positioned off to one side. The holder grips the phone very well and the phone can be removed quickly when you get off the bike. I would say for £20 delivered it's a decent piece of kit. The RAM hardware is extra, of course.