You can already use your iOS device to control compatible devices in your home such as the garage door, thermostat and lighting. Currently each of these services are controlled by their own app, each with its own way of doing things from networking to security. Apple thought it could make things a little easier and is bringing more of these services under one umbrella they call HomeKit.
Working with leaders in home automation like Philips, Skybell, and Honeywell among others, Apple is introducing a common network protocol that will cover these services. With HomeKit users will be able to control their smart locks, lights, cameras, doors, thermostats, plugs, and switches from one app with secure pairing to ensure only your iOS device works.
Services can be controlled individually or grouped together as "scenes." Thanks to Siri integration users will be able to speak a command like "get ready for bed" and have their garage door automatically close, their doors lock, and the thermostat lowered to a nice cool sleeping temperature. As smart home devices become more common HomeKit is a wonderful step towards a future where your home is controlled from the palm of your hand.