Satelite phones and GPS's, by their very nature (communicating with a network of satelites in space), work pretty much anywhere on the planet.

Whether the island is charted or not, the GPS will tell you your unique coordinates on the planet (latitude and longitude, even elevation about sea level). That information, if known accurately, is all the rescuers need to know to come get you.

Even if you're in the South Pacific. I don't imagine it would take much longer than 8 hours for the long-range helicopter to come get you from Hawaii (or Fiji, or Bora Bora, or New Zealand, or whatever civilized place is most appropriate).

Once you've placed the call, how you amuse yourself is up to you... you could always try to catch one of those pigs just for the fun of it. Hey! Anybody remember that joke about the guy stranded on the island with the pig and the dog when Hillary Clinton swims up? <img src="images/graemlins/grin.gif" alt="" />