The Aquarium controllers are pretty neat devices. They will switch either of DC or AC, as it's a relay-type of switch. Once the circuit is made, it'll pass whatever you send through it. However, I'd make sure NOT to exceed the capacity (10Amps I think).
Alternately, someone could rig up a home battery-powered thermostat in their kegerator, run a 12VDC through the switch, and have it activate a relay (the 12V car-type can handle 30A). I used to run a refrigerator that way, never had a problem.