I know they all transmit, but most are at such an extremely low level they don't produce enough RF to cause interference. I was just curious if these did. If I remember right, there is some regulation that states how much RF a device can produce to keep them from causing interference to other devices.
Yeah, turning off a GPS ought be an option made available for those that don't want or need it. As far as I know, mine shuts down during parking mode to save on power consumption. But I keep mine active for the speed indicator.