When I did get into difficulties in the desert, the satellite phone I had with me was invaluable.
They do seem to have another big unforseen use though. I found it very useful as a stage prop. Overlanding in Africa, I had one that was an older model of the 'brick' design, with a big chunky extending aerial. I found that when negotiating with surly corrupt policemen at checkpoints, the satellite phone was great for encouraging them to let me pass unhindered. Having it in my hand seemed to give them the impression that I was far more important than I am, and that I was therefore to be left to continue my journey. Subsequently I found myself reaching for it at every checkpoint. (Mostly Mauritania, Senegal and The Gambia).
I spoke into it often, but only on one occasion was anyone actually connected and talking back to me.