Have you tried
EveryTrail? The pro version for the Iphone costs under $5 and the feature set is impressive.
It allows you to download
free offline topo maps so your smart phone (iphone or android) is a fully functioning GPS away from cell phone coverage.
It will also use Google Earth satellite images...just need to make sure you navigate your trip via Google Earth before you leave so that the image tiles are pre-cached.
And can do realtime position tracking via the web when inside cell-phone coverage too. I have tried a few different smartphone GPS apps and this is the best Ive found so far.
(No connection with the company etc...just like the app...)