draythomp:
Everything that rockwallaby said as well as: There are devices out there that you can control the mains with that are relatively safe, but for us to suggest them, you need to be a little more clear on what you want to do. The ceiling fan, can you point us to an example? What is your mains voltage? If you're using CFL lights or not. Do you only want to control the lights and fan? What kind of fan controller do you have. etc.For example this device can be used to control mains connected devices with an Arduino: Powerswitch tail 2 : ID 268 : $25.95 : Adafruit Industries, Unique & fun DIY electronics and kits
And there are ways to adapt various remote devices to being controlled by an arduino. So, is your fan remote controlled?These are the kinds of things that you need to think about and describe to us so we can make reasonable suggestions.
I will just use the arduino to switch things on and off.
One switch, one fan, one CFL, one tubelight, all this from the already present switch board.