I am plus 1 for spidertracks. I have 21 of them. We have ours set up so that the first alert goes to each pilots cell phone. (We have it set up that if you turn off aircraft power before shutting the unit down, it will generate an SOS signal. If an SOS comes through for the aircraft you just landed, you merely close it by responding to the text and are liable for the first round that night. If no-one closes it, then it goes to tier two SOS.
There is also a "Spider Text" function where you can link a smart phone via bluetooth and text the office through the Iridium, (great for precautionary landings in areas of no cell coverage).