I wonder if a big (Fortune 500) company could get HID devices which were customised so that only company owned devices could be plugged in.. it shouldn't be that hard to design such a device that would show up as a custom device then the installed driver would poke it in a crypto shielded way and it then provides the keyboard/mouse inputs. It can't simply do the standard 'detach and reattach as a HID' because otherwise then a HID would work..

Hm, perhaps.. is anything like that available already?