for me...I'd just turn around on the trail and go back... I always fill up my tank before riding (4 gal gives me about 220 mile range) course that could be the reason I hate the single track with all that damn weight!
but yeah just get a ram mount and a little hand held gps... I used a garmin eTrex Legend for a long time... worked great and it's waterproof. but for long trips the screen is just too small to see when you're on a thumper (vibrations) and you're on hr 14 looking for a place to stop for the night.
Bike looks sweet did you swap in a new headlight (need to scroll back up) that looks like the Acerbis cyclops if I remember right