You could also check out the new version of the Philips Hue Bridge, which adds HomeKit support to an already well-developed smart lighting platform. Any Zigbee bulbs, fixtures or light strips connected to that bridge -- Hue or otherwise -- will work with HomeKit.
For lighting control, the Hue Tap is a great little device that powers itself each time you press a button -- no recharging or battery replacements necessary. Pair it with HomeKit, and you can use it to trigger your smart-home scenes, too.
Another color-changing smart lighting option: this Bluetooth smart bulb from Sylvania, which you can currently get for less than $30 on Amazon. You don't need a hub plugged into your router to use it, either.
You can also keep tabs on the conditions in your home using the Elgato Eve Room sensor, which monitors temperature, humidity and air quality. If you want to take a look at any of those metrics, just ask Siri.
Insteon offers a HomeKit-compatible version of its hub -- hook it up with your router and you'll be able to automate Insteon's switches, sockets and light bulbs right alongside any other HomeKit gadgets you've got installed.
Another lighting option is this HomeKit-compatible kit from Lutron, which comes with two smart plugs that you can plug lamps into, and two remotes. Hook everything up and you'll be able to tell Siri to dim the lights.