I wanted to combine the google kit with a relay board to allow voice controlled power outlets on my Pi 3 model B.
Is it possible to use a relay and the google hats at the same time? I can’t find anything on this elsewhere on the internet.
According to the documentation you should be able to add hardware extensions:
This is a hackable project, so we encourage you to make this project your own!
So I had a look and the "hat" (Hardware Attached on Top) seems to occupy all the GPIO pins on the Pi, but there are some exposed on the hat itself:
From this it looks like you have 4 "driver" pins and 6 "servo" pins that you could use for a relay.