I have my Motorola Droid phone loaded with lots of useful data and maps. If I have cell signal, I have almost unlimited access to whatever data I need. If not, I still have GPS, a magnetometer, lights, a camera, and apps that can work with the data already on the phone.
I can charge it from AA batteries using a gadget from Energizer, or I can charge it from my Solio solar charger. As long a I have my EDC bag or GHB I will have one or both of these.
Even when this has become the "old phone" and is no longer on a data plan with my cell provider, it will still be able to use a WiFi connection to access the internet, thus still being a useful gadget even after it has been replaced as my EDC cell phone.