App that allows iPhones to share information while overseas without a plan (and no data)
You could try something like FireChat. I have not tried it personally, but it is touted as "a new way to chat: 'off-the-grid'." It uses iOS 7's mesh networking capabilities to achieve this.


  Now you can chat with people around you – even if there is no Internet
  connection or mobile phone coverage.
  
  Whether you’re on the beach or in the subway, at a big game or a trade
  show, camping in the wild or at a concert, or even travelling abroad,
  simply fire up the app with a friend or two and find out who else is
  there.


[...]


Instantly chat with anyone around you on iPhone, iPad, or iPod touch
Works even without any Internet connection or mobile phone coverage 
Use the "Nearby" mode for off-the-grid communications, up to 200 feet of your location
Multi-hop capabilities extend the range of peer-to-peer communications