It does not need cell service. They work just about any place in the world. In my opinion a SPOT is a must for any one that goes way out off trail or even miles on trails especially alone. Many many people over the years that got lost or hurt would have been rescued earlier, found faster and may have survived if they had a spot. I have been involved In a few search and rescues over the years and no one had a spot. If they had they would have been home for dinner instead of spending days in the wild.
I have zero affiliation with them this is just my experience.
That is correct or the good thing about the spot is you can get it per month so if you only want to pay for one month say October during deer season you can get that one month instead of all twelve months .