Is it possible to detect two Gear VR controllers at once with Unity? Is it possible to detect two of the Gear VR controllers at once, with programming in Unity? Has anyone heard of any way to do this, or does Oculus limits it to inspire you to get a Rift? It would open a whole world of possibilities for the Gear VR when used with Unreal or Unity.
Check this post on Oculus developers forums: Would I connect two GearVR Controllers?

User imperativity, listed as "Oculus Staff" in the forums answered the following on 2017 May 1st:


  Yes, there is support for using two controllers at once.
  This functionality will be released in the future and is currently not
  available at this time.


Last blog post about the controller mentions that single controller is supported by several version of Unity starting from 5.3.

According to the documentation, the API provides a way to differentiate between controller held in left hand and in right hand:

OVRInput.Controller.LTrackedRemote
OVRInput.Controller.RTrackedRemote


The feature is not currently exposed by Oculus SDK, but officially it will happen soon.
When it is exposed, it is probable that Unity will support it soon after, maybe through the APIs mentioned above.