(Mobile/Android Customization Question) Toggling other user's video source

Hi everyone, I’m trying to implement a custom feature, would like to ask for your advice.

Two people are on the call, the first (A) is on mobile client, the second (B) is on web client. I need B to be able to toggle A’s video source (switch between smartphone cameras).

Looking for the quickest solution. What’s the easiest way to achieve this?