Apps to see myself whilst filming?

Hi, 

Another noob question;

So when I'm filming myself with the main camera on my phone (not the selfie cam), is there an app that will allow me to see what I'm filming without having to look at the phone screen itself? Because it's obviously not practical sometimes.

So an app to mirror onto my other phone (the one I'm not filming with) or laptop?

Hopefully everyone can understand the question that I'm asking 😕😕

Cheers 🍻