Wrist Wrap For SmartPhone

See link for "wristlet armor". There is a specific word for that type of forearm accessory, that I've been trying to remember. "Braces", maybe.

Anyway, they are plenty large enough that a smartphone could be mounted on one, so its length stretches along your forearm.

You wear it kind-of like a wristwatch. As a bonus, if you are wearing a jacket or other clothing that is covered with solar cells (resembling "scale" armor), you can provide plenty of power to the smartphone, so its battery doesn't run down.

As another bonus, you could obtain a smartphone app that uses the phone's build-in motion sensors to detect when your arm moves from the "dangling" position to the about-to-be-used position, and the app would display the current time and perhaps other default stuff on the screen.