capturing input from multiple computers

Question

i would like a program on computer A to be able to track the keyboard input on computer B and computer C through a trace() or print() method.

Not specific on which language, although i am most familiar with flash/processing or php, something like that.

this is for an installation i am doing at work; note that this is similar to a keylogger in function but it will be at work on our network and controlled by me. I will have access to all computers involved.

*EDIT - the arduino ethernet shield looks like it might be something that would help in this...? kind of NOOB in this area.

thanks!