How Do You Get Google Cardboard to Read a Continuous Press?

I'm doing a VR shooter game and was hoping to have an automatic mode where the player could just hold down the trigger and fire continuously, but it seems like even if I use Input.GetButton (as opposed to Input.GetButtonDown), my Google Cardboard headsets (Viewmaster and Dodocase) only read the initial press, so it only fires one shot. Yet if I physically touch the screen with my finger, it reads the continuous press and fires continuously.

Anyone know how to achieve this with a Google Cardboard trigger?

Thanks!