Google Cardboard + GazeInputModule: Capture trigger when not activated over UI

Hi everyone!

I'm developing a toy object visualizer with Google VR (specifically Cardboard). I'm using the default GazeInputModule to allow the player to interact with the app UI. When the reticle is not over a UI element, and the trigger is held pressed, I'd like it to cause the camera to rotate around the center of the object that's being looked at when the user moves his head (instead of rotating around its own center).

I think I'll manage the camera movement; my problem is I don't know how to check whether the trigger is pressed and it's not already activating some UI element. How would one go about doing that?

I'm new to Unity so this may be a stupid question, sorry :)