come on, a cell phone would be useless unless you were in signal range, and i tell you where i go every year, a cell would be useless, i do have a two way radio with me in my vehicle though, to radio help or to the logging trucks that might be going by, but of course if i injured myself while walking and i wasnt near my vehicle then the radio would be useless too. i think the whistle or horn would be a good idea, as well as shooting three shots, carry enough ammo to keep shooting the shots for a while, then people might figure out that you werent just a bad shot.