There's other streamers for phones which I think are free or cheaper (maybe even for Vive and Occulus too?) that support SBS out of the box too, so that should be a solution that works with most rendering-wise.
As for taking input, the Trinus plugin is just one of probably many different ways of getting the Gyroscope information back to the app. I think I've heard KinoVR works well, but not sure how that would be implemented in Unity.