Kokua Line: Can I drive with cell phone or not?

Question: I’m hoping for some clarification on the Hawaii law that says we cannot use cellphones while driving (I was living on the mainland when this went into effect so I don’t know the details). I’ve asked several people and received different answers. I often rely on my cellphone GPS to direct me to my destination. Are we not allowed to use it for this purpose? Is it legal to mount my cellphone on the front windshield? On a related topic: I thought it was illegal to drive w