Garmin Etrex GPS
I use a Garmin Etrex Summit GPS which does all of the normal GPS tracking plus altimeter, tide chart, sun/moon charts, hunt/fish charts, electric compass, trip computer, elevation profiling, backlighting, and barometer. I have a quality window mount made by RAM mounts and a handlebar mount for the dirt bike and mountain bike, plus it is small enough to drop in your pocket when you want to get out and hike or follow a stream to look for a good spot.
One of the best things about this type of GPS is that it has memory which will allow you to remember spots of interest, create routes with waypoints, or interface with your computer to create trip profiles, or even look back at the elevation profile of that last 20 mile grade.
Too much to list here, but for the $285 that I paid for the GPS it is one of the best toys I own.