I'm not sure what NGUI, as a UI system, would have to do with VR input? Do you mean have it react to input from the controller itself? If so, you can do anything you want just by assigning a custom input function (UICamera.onCustomInput) or just overriding NGUI's input functions (UICamera.GetTouchXXX, UICamera.GetKeyUp/Down, UICamera.GetMouse, UICamera.GetAxis, etc).
