A simple screen sharing module and the presenter or the viewer can take control of the screen.
No installation should be there. Just A hosted solution.
It should be like this..A person logs into the app. and sees a button "Host Show your screen".
When he presses the button, he gets a link and a pin which he provides to his viewers.
option2: "show universally" where he gets a link and no pin is required by the viewer
need asap. If u have something similar already written perhaps it would work with some modifications