The only eligible test device so far has been the Nexus 6P, and even that came with the caveat that it would run quite hot and “thermally throttle CPU and GPU performance after a short period of use, depending on workload,” according to Google’s developer documentation.
The VR SDK supports both Google’s Cardboard and Daydream efforts. The latter includes a proprietary controller that Google developed in partnership with Unity and Unreal for native integration.
Count on the upcoming Google Pixel phones to be Daydream compatible, which would give Google a chance to showcase the platform on its latest hardware. Google says several Daydream-ready phones will be on the market by year's end.
Google is keeping fairly tight control over who gets in to the Daydream Access Program, which requires an application to join.
Why this matters: We sure heard a lot about VR at Google I/O, but there hasn’t been much to see afterwards about what the Daydream platform will be like. Now that developers can get more deeply involved, we could have some actual apps ready for when we get some Daydream-compatible phones. Either way Google has some catching up to do with Samsung’s Gear VR platform, which is already on its second iteration.