Currently, ARCore is still in beta. This means that this project only work using the Samsung S8 and latest GearVR. In order to get positional tracking, the camera must be exposed and your environment must be well lit and have a wide number of features to detect. As such, this project will NOT work on Daydream. However, you may be able to get this to work on Google Cardboard with a headset that exposes the camera.
If you would like a run down of the project, watch this video : https://www.youtube.com/watch?v=4EWPUdE_kqU