Once an application/game has been created it should be possible to interact with it from another computer/controller. This could be via Serial Port, Modem, Radio Modem in addition to hooking up to the Net. Various methods/protocols could be used.

If any one out there has ever used XPlane they may be aware that a separate control system can be built using another computer and aircraft (on the first computer) flown using the separate (custom control panael) from the second computer via ethernet using the UDP protocol.

check out the next generation Blender project. It's the best solution propsed for interactivity so far.