I highly doubt that this is the case. The law is meant to stop people SMSing or taking photos with their phone (i.e. touch it). It is not meant to stop the phone sitting on your dash, effectively running a screensaver. By your definition of 'use', you are 'using' your phone whenever it is turned on - because it makes you available for others to call, therefore providing functionality. I agree that people should not interact with their phone when driving, for whatever reason. but following a preset GPS route does not require interaction.

Besides, how is the cop going to know? if you have your phone in a holder on the dash (which is legal). Its not like he's going to notice unless you start fiddling with it, rerouting while he's handing you your speeding ticket (which would be extremely stupid)