Timofte Andrei shows us how he built his Arduino Home Automation System. The video below is in Romanian but with the English Instructable and video overview you can get a good idea of what is going on. He has went all out and built an Arduino clone for the brain of the system.
 “For this project I’ve used:
1. An Arduino clone
2. SIM900 GSM SHIELD
3. Relay module
4. 2×16 LCD Display
5. DS18B20 temperature sensor
6. Push button
7. Some Dupont wires
8. A led module (this is optional, if you have a chinese relay module with built in LEDs)
9. Some nuts and bolts to mount everything in place
10. A wooden chopping board or other kind of wooden board for propper display of the components”