Oh man, I didn't see this yesterday. If that is true then you definitely want a GPS App on a phone. Any of the real navigation Apps (not the standard GE or Mapquest etc. but something like Gaia or MotionX or Scenic, or Osmand etc etc) will do exactly that. Without a cell signal. Without even a calling plan. Even a cheapo eBay phone for $50 or your last phone that has been sitting in a drawer since you upgraded to your current phone will do exactly what you want way easier and cheaper than any gps unit. Don't worry, you don't have to use any of the other 1000 things a smart phone will do that a gps can't.