Cell based GPS doesn't always work, I've been without it places in New Mexico and Death valley. I noticed if you start a trip while in cell coverage you can sometimes make it through a dead zone but if you try and start a trip in a dead zone it's a no-go. Something to think about it you like to go off the beaten path and who that owns a Jeep doesn't? I used to carry my old Magellan Satellite GPS for that reason but I also believe in maps and a compass.