I believe for it to affect other phones in the vehicle other than the drivers, they would also have to have the app loaded onto their phones. If I am thinking correctly, it would act much like the systems that come with the cars already for hands free driving, accept this will have a certain amount of control over the phones with the apps installed and synced with the cars hardware unit. If the app is not installed on the passengers phones and synced, I am guessing it will not affect their phones. IMO.