Was driving up the coast with family. No cell signal for long stretches. At a stop, went to send a message to my wife who had walked over to a grocery store. iPhone said SOS only, but offered to send via sattelite. Didn't realize it was an option. Sure, why not.

So it had me stand outside and twirl around like an idiot until it said it had a signal lock. Pretty cool animated globe graphics. I hit 'retry' to send the message.

Fail.

Turns out it only works if the recipient is also reachable right at that point. Doesn't queue it up for later transmit or anything. Lesson: be careful if out hiking in the woods and sending emergency messages for help. Make sure you try more than one person.