Christopher of CDeutsch's Blog has gotten to making Siri a whole lot more useful around the house, integrated voice activation into his home automation controls, a setup so easy his young daughter can turn on and off the fan using the iPhone by calling upon the help of "Gladys" (any Portal fans out there?).
I've created a Twilio, Node.js mash up that allows me to control appliances and the thermostat in my house using the iPhone 4S's Siri voice recognition.
I have a Mac Mini I use as a server which is connected to the PowerLinc Modem via USB. The Indigo software communicates two-way with the Insteon devices in my home via the PowerLinc. In addition to a native iPhone app, the Indigo software has both a web interface and RESTful Api you can use to control your device
Check out the complete description fo Christopher's project over at his blog post, Using Siri For Home Automation.