There is some great work here - BUT you can now add "OK Google" to the cardboard AIY using official Google software !!!
I followed this -http://eduncan911.com/stem/embedded/aiy-google-assistant-upgrades-may-2017.html
and it works as well as the Google Assistant (no delays) but has the AIY advantage of software that Lesson 1 people like me can use to control local GPIO etc.
I had previously followed -http://www.androidauthority.com/build-google-assistant-raspberry-pi-770296/
so as to use a USB microphone and TV speaker.
If you do that first you have to restore the modified check_audio.py file by doing -
cp /home/pi/voice-recognizer-raspi/checkpoints/check_audio.py /home/pi/voice-recognizer-raspi/checkpoints/check_audio.py~
git checkout /home/pi/voice-recognizer-raspi/checkpoints/check_audio.py
Then restore it later - I guess you could do all the USB microphone changes after getting "OK Google" installed - not tested.
There are several other upgrades. eg Use a wav ping sound instead of the LED.
I have not tried that yet