I see two possibilities:
1. VNC, which will be slow
2. Wireless USB mouse and keyboard, which may not have enough range, depending on how far away the second room is, and some sort of wireless VGA (or DVI?) broadcaster. The challenge with that will be finding such a broadcaster that is system-independent (i.e., no drivers required), is not absurdly expensive, and exists. It seems like the kind of thing that should exist, but I'm not sure it does.
