“Try going to northern Arizona where there is no cell service. All you see is your car’s marker on a grid”
Download your own “offline maps” before the trip using Google Maps or Google Maps for iPhone or something similar.
Garmons are better GPS devices than any phone. Paper maps are still the best. There are many failure points for GPS navigation, none for maps and compass. (Except old fashioned brain farts.) I’m very fond of USGS Quads. When I travel I always bring Delmore map books along, one for each state I visit. They help find more interesting places than Internet searches can turn up.