Want your lights to come on before you get home? Turn down your thermostat after you’ve left for vacation? You can always use your accessory’s app, but if you have iOS 9 or an Apple TV, you can also use Siri commands when you’re out and about.
Starting with iOS 9, your iPhone can securely chat with your HomeKit bridges and accessories even while out of the house. It can do so because of the new HomeKit Accessory Protocol (HAP), which uses secure networking over iCloud to talk to your connected HomeKit accessories. HAP doesn’t work with prior versions of Apple’s mobile operating system; as such, if you’re still using iOS 8, you’ll still need to use and set up an Apple TV for controlling your house outside your local Wi-Fi network.
If you’re still running iOS 8 or your accessory isn’t compatible with HAP, you can use a third-generation Apple TV. Here’s how:
More info at http://goo.gl/GJMVc8