Some money in the proper currency surely helps. The smartphone also helps to acquire current information on actual policy and policy changes. In some countries the Dublin regulations are not enforced that rigidly. Even Germany announced that they will not bother to check migrants from certain countries. That might influence the decission whether and when ID papers should be "lost".

Smartphone is basically a computer. There are a plethora of usefull survival tools available in the app store. I'm keeping a huge library of survival books and articles on it. For connectivity without cell coverage - make sure you have the FireChat installed. It allows ad hock link to other FireChat members, which might help to create a communication mesh network if people are within a WiFi range of each other.

For the data storage and power - I will never ever buy a smartphone without SD card slot or without removable battery. However, I have this little thing on my EDC keychain: http://goo.gl/KJG8sv (eBay). It's a unique short flexible USB charging cable with integrated card reader, switchable to OTG mode. With it you can charge your phone from a USB port, use it as a USB flash drive (I have a 64Gb card in it), transfer files from the card to the phone and back (or just read it on the phone), as well as transfer files from the phone to the computer and back (sync cable).

It has survived 8 months (including a beach vacation, 3 camping trips, and 2 hiking trips so far) in my pockets with keys and other gear. Would recommend! Oh, and it's also a dim red flashlight.