As a non tech guy I've got a related question. Can you just connect these devices with a cable? Blue tooth uses a bit of power in both devices, so turning it off should save some juice.
No...they cannot be connected via cable, but the inReach can be used to full-function as a stand-alone unit. The Earthmate app can also be operated on the phone without having the inReach turned on, but not all functionality is available that way.