Sending input to external device

[Lv0f92yv]

I have two laptops, running linux. Each laptop supports at most 2 outputs (onboard monitor plus one external). I would like to use one of the laptops as a third display (sort of).

I am thinking of using one of the laptops as a server that waits for input from (mice, keyboard) coming from the other computer. I want to run an application on the primary computer that can (when say, the ctrl input is down), sends whatever input I give it to the second computer (who is of course waiting for it).

I realize there are some inherent problems/inconveniences with this, but I think it would be a neat idea anyway.

I would do it in Java (using their Robot class), but something tells me that Java doesn't allow for the OS-level stuff I would need to do to capture input without the main application being in focus.

Is this possible?
Is there a better way?