The DeLorme PN-40 is a great GPS primarily intended for hikers, but it is waterproof and the power plug can be used in rainstorms in an open Jeep. You can import gpx tracks and more from your friends, so even if you haven’t run a trail before you can do so with confidence. It can be made to do on-road directions, but it isn’t very good at it. It takes a long time to redirect if you miss a turn, and the small screen means all but the most eagle-eyed will find it hard to see when moving at highway speeds. Current model is the PN-60.