How to organize checking the presence of a user in a room on a mobile application?

Question

JavaScript

What is the best way to check in a Nativescript mobile app that a user is nearby?
I plan to put a tablet where the application will display information when the user is nearby.
But if the user is not in the room, I would like to turn off the screen after a while, and when he enters, turn on the screen.
What is the best way to organize a check that the user is nearby?
Listening to the microphone, camera, or how is it generally done so that the user does not press any buttons and the application turns on?

Answer 1

If the application is not in the background and the device is not blocked, then as you wish.
If the application is in the background, then no way, because a limited list of activities is available to the application in the background.
If the device is blocked - then no matter how.