Drawing overlay on screen from output of another computer

[R4k4n0th]

I know that I can get data from another computer (via ethernet cable, or USB cable etc.) and draw the overlay in the computer that I am using locally but that is not what I want. I do not want any software involvement in the computer that I am using.
I am wondering if I can draw overlay with the help of a projector or by combining video outputs from two computers into a single display. Is there such a project or a method that you know of?

 

[newtekie1]

Two projectors pointed at the same screen.

 

[R4k4n0th]

Two projectors pointed at the same screen.

Is it possible to do it with a single projector? For example, as I am playing the game, the projector will draw the overlay onto my gaming monitor. I am wondering if this is possible.