I purchased this device as a sort of insurance policy for the possibility of getting injured on a run or hike and being far away from a vehicle (and likely far away from other people). It communicates with a search and rescue satellite network and when activated can transmit your current location (using GPS), whereupon your local rescue services are notified. I hope I never have to use it, but I am happy that I have it. It's also occurred to me that I may end up using it to help someone else out, so that's another potentially beneficial reason to carry it.