Smart Home technology has been around for a long time but due to a combination of price and complexity it has generally only been available to a limited few. Apple's HomeKit, which makes these devices controllable by Siri is trying to, at the very least, deal with the complexity issue. While the list of products that work with the system is still fairly limited they just added a major new component.
The Ecobee3 is a $249 smart thermostat which competes with the better known Nest product. The network device is able to learn the habits of a household in regards to temperature and make adjustments on its own with the goal of saving a homeowner money. Apple stores will now be carrying a special version of the Ecobee3 which includes the HomeKit functionality. Now you can make adjustments to your thermostat simply by telling Siri to make the adjustments for you.
In addition to being able to control an individual device directly, HomeKit also allows for home automation and system integration. In combination with another HomeKit compatible system, like Lutron's Caseta lighting control, you can tell Siri to activate the "away" scene, which would turn off all the lights and lower the thermostat all at once. Most home automation systems require large central hubs to act as a brain in order to conduct that sort of automation. All HomeKit requires is a $69 Apple TV.
It's far too early to tell if HomeKit is truly the system that will bring the connected home to the masses. There is still a lot they need to add to have all the pieces they need, however if they keep heading in this direction the "home of the future" may be closer (and more affordable) than expected.