Siri is much smarter in iOS 9 - but would you trust her to oversee your connected home? That's your call to make, but if you want to give her a first test, you can do so with the new bridge for Philips' Hue lightbulbs.
Announced last October, the new Philips Hue Bridge 2.0 is Apple HomeKit and iOS 9 enabled, meaning you can use Siri and other HomeKit-enabled apps to control the various Hue smart bulbs. While the new bridge is required to tap into Siri and HomeKit, thankfully all existing bulbs and lamps will work just fine.
HomeKit makes it easy to control an array of connected devices using the same framework, and it also means you can, for example, tell Siri to "wake up" your home and have it tweak both your lighting and thermostat at the same time. Or have it turn off the lights and lock your front door - another example that Philips says makes the new bridge advantageous for Apple users.
And even if you're just sticking with connected lights, you'll have plenty of options. You can ask to have a particular lamp or light in the house illuminated or dimmed to a certain degree, or activate a certain lighting "scene" mode as desired. (UPDATE 7/10/15: Note that adding Hue bulbs to a "scene" can only be done via other HomeKit apps like iDevices Connected or Insteon, not through the official Hue app itself. The Hue app doesn't support the full HomeKit framework at present.)
The Hue Bridge 2.0 - with its new rounded rectangular design - is now on sale, but Philips says anyone with the original, circular bridge can get a 33% discount off the new purchase from meethue.com. But if you have the original bridge and you don't need HomeKit support, don't sweat the upgrade: Philips says it will continue to support and update the original bridge.
And if you do grab the Bridge 2.0 and decide not to stick with HomeKit, Philips says it's "future-proof" and can be updated to support multiple connected home platforms, including Samsung's Smart Things and Nest Weave.