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.