Start app with a service or notification

I want to make a panic button that when this is activated or start the application on all devices and emits a sound etc. ionic 3

You can try with Native Audio (more info about it).

Then if you want to do on start, focus on

platform.ready().then(() => {
})

on your app.component.ts.

If you want it on click, just do

<button (click)=“panicAudio()”>

And put your Native Audio inside panicAudio() function in your .ts

from the same app by pressing a button this activates the same app on all devices, like when I make a phone call and activates the phone app on another device