the simplest way would be to get a microcontroller (like an arduino, or something else cheap and easy to program) to listen to the serial port of the GS and solid state relays appropriate for the input voltage, and switching voltage current. Just like using any other computer, you make a program, have it send out commands, which the micro reads and acts upon.
you could get a bit more fancy and find some outputs on the computer itself and bit bang those (like a card slot) but you still have to have some way to isolate the fragile brains from the brute force of mains, SSR's are usually the easiest way ... though if you dont shop around they can bite you in terms of cost.