Factually it does not just do mouse simulation-- I mainly use it for chess-playing and for a multimedia CD so I only require a good mouse (that I'm used to). The simulator does do keyboard simulation, joystick simulation of various types, and Atari disk drive simulation as well all using one cable. Here you can probably get it for less than regular price at:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=ADME:L:LCA:US:11&item=320063617383If you add the weight of all the devices it simulates, they would be well over the 4lbs or even 7 lbs laptop. If you have a laptop that supports an overlay video window, you can replace your composite monitor with the PC-based laptop as well-- now there's a big savings in weight. MPDOS will support live video window in overlay mode as long as it's Video For Windows compatible.