Well the good thing is, you don't actually need signal once you buy the app. You just need to buy it while you have internet coverage, which downloads the app to your phone and then you can access it offline as much as you want once you're in the wilderness. As long as you remember to charge your phone, you're good to go!

The SAS Survival Guide is also available for the Android and Windows Phones

Android : https://market.android.com/details?id=com.trellisys.sas

WP7 : www.windowsphone.com/en-US/apps/0153f6c4-ac7c-e011-986b-78e7d1fa76f8

There is one survival tip that my grandfather said would work in just about every area of the USA to get you rescued except in the desert and really barren areas......he said always carry a knife and a pack of water proof matches with you,,and if you get stranded just start a small fire and see which way the wind is blowing then start moving in the opposite direction and as you move begin to set other small fire along the way,,soon you will have about an acre of area on fire and someone somewhere will see the all the smoke and people will come to put it out and you will be rescued......then you just have to say that your signal fire got away from you cause setting big fires on purpose is illegal

you can get some great apps for your iphone from recombu