The kit, available here for Android, has native Unity integration and native integration with Unreal Engine 4.
Daydream is coming this fall, and is part of the Android Nougat release. A number of apps are already slated to be available at launch, including Netflix, Hulu, HBO, Imax, MLB, the NBA, CNN, The New York Times and The Wall Street Journal. Some of these are currently only available for the competing Oculus platform and the Samsung Gear VR.
In addition to the new app, the Daydream platform also promises better performance, graphics, and sensors, and also has a virtual home environment that eliminates the need to take the phone out of the viewer whenever the user wants to switch apps or load up a new video.
Google is expected to talk more about the platform at its October 4 event.