HomeKit, is the name for Apple's home automation framework. With HomeKit, Apple devices have a standardized way to configure, communicate with, and control "the internet of things", including connected lights, speakers, scales, security systems, and more. You can even group actions together and trigger them using Siri, Apple's virtual personal assistant. So, for example, you could say "crash the compound" and HomeKit-compatible devices would make sure your garage is closed, your doors are locked, your lights and music are off, and your coffee machine is set to help wake you up in the morning.
If you have a current generation Apple TV running current generation software (7.0 or later), you can even use Siri to control your HomeKit accessories when you're away from home.
Apple announced HomeKit at WWDC in June of 2014 and launched the HomeKit part of the Made For iPhone (MFI) program in November. Accessory makers need to submit plans and prototypes for MFI approval and, if they follow the proper API guidelines including end-to-end security encryption, they get certification and the MFI logos for placement on their packaging.
Numerous HomeKit products were shown off at CES in January of 2015. The first wave became available for order and pre-order on June 2, 2015.