Want to write an Android app?

Question

Android

When the application is installed on several devices and they (devices) fall within a distance of less, for example, 10m from each other, a graphical and sound notification is produced.
How to implement this, ideas?
Apparently, we need a remote server where coordinates from applications will be sent. Will they compare in some way?
Are there ready-made solutions? I have basic knowledge in writing simple applications for this OS.

Answer 1

I see it like this:
1) Request permission to get coordinates
2) Start the service and constantly get coordinates
3) Send coordinates to the server
4) If the coordinates on the server are close to each other, send push to both devices
5) Receive push on the device and inform the user