Evelyn nails it as usual.
In an emergency, think: Cheap. Simple. Ubiquitous.
Perhaps cellphone SMS messages that go directly to a central wiki that is hosted by an large easy-to-remember-even-if-I-never-imagined-I-would-be-in-a-major-disaster organization whether it is Red Cross or Google?
What would have been helpful in the tsunami was a central phone number everyone has memorized to call in case of emergencies. I don't know if they have 911 in other countries. After the tsunami, people (those on boats, and high ground) still had cellphones. But no one knew who to call.
We managed to get to high ground eventually and find a resort with a working television set. Yet, there was absolutely no usable information for survivors. Ah, now I know a 8.9 earthquake hit. More photos of devastation. Hmm, tsunami. That explains the wall of water we frantically ran from. But it's all retrospective. And of little practical use.
We wanted to know if another wave was coming. Were there aftershocks? Which hospitals weren't damaged - i.e. do attempt to flag a boat to Krabi or Phuket hospital? Will we need money for medical care (i.e. now officially destitute in a foreign country)? It'd be nice if there was ONE television station you can turn to for survivor information.