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Voice recognition is no longer in infancy, especially since Siri just launched on the new iPhone 4S (although similar technology is available on Android too. This project shows you how to use it to automate your home without spending big bucks.

The core of this project is a VRBot speech recognition module.  Next, the project creator used some low-cost wireless light switches (you could also use relays).  The VRBot speech recognition module recognizes 32 custom voice commands.  Once a command is recognized, a wireless switch is activated via a radio receiver.  The setup is simple after you spend some time understanding the wireless communication protocol between the different modules.  See the project blog to engineer the whole thing yourself.