Iridium disappointment--but maybe not

Today sartorias posted a link to this post by an adventurer. I've only glanced through it so far (thinking oooh! rhodolite! oooh! penguin!--yes, I go from picture to picture), but my eyes were caught by this line, from when the author is adventuring in Antactica:

then you can borrow the iridium phone

And I thought, iridium phone? what is? Iridium powered? Made of iridium? (what exactly does iridium do? what are its properties?)

And this being the Internet, it was easy to discover that while irid...