I have had quite a bit of experience with KVMs, both PS/2 and USB.
In several cases, the PS/2 keyboard and mouse did not connect properly when switching from one machine to the other.
Admittedly, all my machines were desktops, not laptops.
Due to the above, I have a vague suspicion that a wireless keyboard is not going to work, but who knows?
What you are looking for would be this: http://www.geeks.com/details.asp?invtid ... DT&cat=KYB
Not currently in stock there, but available elsewhere, e.g. here: http://www.amazon.com/IBM-USB-Keyboard- ... B00009APTK
Quite a price difference...