Wireless 802.15.4 Reactor Relay
Trigger Relays Automatically Based on Inputs

Take all the Power of the Reactor Series Relay Controllers
...add a Digi Wireless 802.15.4 Compliant Interface: 
Configure Wirelessly, Trigger Automatically!

It works like this.  Plug our Wireless 802.15.4 modem  into the USB Port of your computer.  The modem will mount as a COM port on your PC.  Open the COM port and start sending data to the modem.  The modem will forward your data to all Wireless 802.15.4 compliant devices within range (it is also possible to speak to a specific device when other controllers are in range).  Modem descriptions are at the bottom of the page and can be purchased at checkout of this Reactor board.