MSG

In the middle of a crowd, get MSG and show others where you are.
All silent at night, communicate with MSG.
Far away in a mountain, no network coverage... use MSG.
Use it inside a box and point it to your peer so only both of you can see it.

Just for fun: use MSG.

This app allows you to display messages using letters that fill the whole screen so it can be seen from the distance.

It also allows to create a human screen where each one holds one changing letter of a message on their device.