This plugin uses a sensor fusion approach developed by Alexander Pacha, similar to Google Cardboard but better.
Different derived sensor models are made by combining the phones sensors (accelerometer, gyro, compass) in various combinations.
These derived sensors are then fed into a higher lever fusion filter to yield the final signal which has less latency and greater accuracy than Google Cardboard.
Using the plugin is simple, after importing the plugin you simply initialize it once and then call a function every frame to get the estimated device rotation, then directly apply this rotation to the camera.
Full concise instructions are provided with the plugin, along with a function to get stereo rendering working.
With this plugin you can produce the best vanilla Android VR experience possible.
Take the demo APK for a spin on your phone:
Tap the screen to toggle tracking modes between "Responsive" and "Accurate"