Now its as much as you what you need to govern, for example in case you need to show the lighting on and of you could use relays, in case you want to alter the brightness of the lamp you may make a dimmer with MOSFET as proven on this instructable so with that you will be capable of manipulate the speed of ceiling fan, excessive strength halogen or heater.

Be careful while connecting any inductive load on the circuit, recollect to use a Flyback diode while doing so.