I have been looking at various sources looking for ideas to incorporate into my project.
I am breaking my research into 4 areas; getting keystrokes/mouse movements into the master arduino, getting the keystrokes/mouse movements Out to the slave, receiving the output on the slave, and sending that out to the target machine.
I have briefly used i2c communication before and have used an Atmega32u4 for keyboard output in the past so I am focusing on how to read PS2 input I have attached a link to a fantastic project which creates a DIY shield for an Uno.
It also states that this shield should still work if USB>PS2 adaptors are used, so i may build them into my final design. USB keyboards are much more common these days.