Frankly, Im too ancient to do back country biking, or even much hiking, but this app work insanely well at higher speed activities. 4x4, quad, single track, it doesnt matter. Perfect tracking on downloaded maps, or if in an area you havent prepared for, it tracks you and lets you follow your way back with a map, which downloads the minute you get cell coverage. Totally awesome.
Furthermore, you can switch to satellite imagery or any number of other map types, export either live (if cell service) or after the fact, along with seeing elevation gains and losses either superimposed over speeds or separately.
There are so many more features I havent even tried yet, but what I have done gets a rousing cheer of congratulations from me.
Aspie about MotionX GPS, v22.0