I have an ionic 3 app that I created for video conferencing. The problem is if the other party is not online, I can call him. I want to be able to do offline calls wherein if the other party is not online, I can call him and his app will open and display the call just like skype or whatsapp. Can ionic able to do that and if so can someone send me a sample code? If not, what is the workaround?
I think you need a plugin for that.
If you don’t find one you could always make your own.
I could imagine that you have a notification with a special sound triggered in real-time(as for example over Ionic Push or Firebase).
But I think you meant an overlay that could be more difficult:
you could keep digging the internet
or just start to write your own Cordova plugin for this purpose. (on android are overlays definitely possible, but I have my concerns about overlays on iOS)