Is it possible to have one PC masquerade as an HID keyboard or mouse and have its output control another computer via PS/2 or USB port?

I'm not talking about using IP broadcast key information and then inject keystrokes using client software on the slave PCs.

In this scheme there would be no required client software at all, and the process would be totally transparent to the slave PCs. As far as the slave PCs are concerned, they only see a peripheral connection from your average keyboard.

Obviously this would require some software driver programming on the master PC emulating the HID, which I can play around with. What I'm more interested in is which interfaces this would be possible on.

ie.
Master ---> Slave
serial ---> PS/2?
USB ---> PS/2?
USB ---> USB?

I just had this thought last night, not sure if it's feasible. Please don't suggest any fully software solutions. I'm wondering about the feasibility of this particular idea.