Post is TBD:

Most Trekkers use a dedicated GPS device, but some have successfully used a cell phone for primary navigation. It is a trade-off….

Dedicated GPS more rugged, can be more outdoor visible and better reception,

Cell phone cheaper, lighter and more informative.

Input:

http://www.consumerreports.org/cro/news/2010/10/faceoff-gps-navigator-vs-cell-phone-navigation/index.htm

http://www.advrider.com/forums/showthread.php?t=936814

 

 

For Phone mount, here is a proven one…

RAM X-Grip Cell phone Mount

RAM X-grip

 

Cell phone reliability is lowered by rain, so you can put cell phone in Water/Dust Protective Case

Iphone Otterbox Case

 

Here is a handy accessory

USB+Cigarette Power Handlebar Jack

Cig+USB handlbar power

Most popular nav. software seems to be Gaia, but there are many.  Make sure it supports off-line maps and track logging.