I'm going to add to the tips for choosing the right phone card for you.
-Choose a phone card that can be used internationally. Not every card can be used both to and from domestic locations (within the U.S. and it's territories) and both to and from other countries. You never know where an emergency may happen or where an emergency may take you.

I'm also going to add to the tips for using phone cards
-You can barter for goods using telephone talk time. This goes against my ethics for emergency situations, but the fact is it is another way of using a phone card. If you find yourself in a situation where you have no other means of trade you may be able to trade using the phone card. DO NOT trade the actual card, the toll free access number, or the PIN. Arrange for an amount of time for the person that wants to trade with you to talk on the phone. You dial in the toll free access number and PIN making sure no one can see what you are dialing. Let the person that wants to trade with you dial his/her number. You time the call. Make the trade.

I will go ahead and add this information to my original post.