Recently, it seems the assistant on the Pixel has received smart home capabilities. The capabilities are currently limited to the same home services that are available on Google Home. In the Pixel assistant settings, there is now a Home Control menu option where you can connect WeMo, Honeywell, Nest, Phillips Hue and SmartThings devices so you can control them from the Pixel.
You can control other items from the Pixel Assistant using IFTTT as I have written about before here.
The process for connecting your services to the Pixel assistant are pretty straight forward. Just go to settings in the assistant, choose home control, and then press the + sign to connect. Select the service and follow the instructions. Below are screen shots of the process for setting up WeMo, as that is the only service I am currently using. After you have the service connected you can create rooms and assign devices to a room so you can control the entire room at once.
I think this is a huge move forward and feel this is a great indication of things to come for the concept of one assistant across all devices.