I've been using one for about 2 years. As stated, it's another tool but not a guarantee.
I have found that I could get a signal out 90% of the time- sometimes it would not show a "connection" after I had sent a message but remained on the move, but if I stopped It would show it connecting ok and going through.
Like leaving info at home/w/loved ones about where you are going, I found it is also important to have a protocol with my wife- how many times/when I would use the check in feature, and how long she should wait without receiving a check in before getting worried.
Her concern is that something happens where I lose the ability to signal- knock my head, killed by pirates etc. Thus I don't send an I'm ok, nor do I send a help/911 message.
My worry- is That I have backpacked in umpteen miles, its getting dark/I finally found the animal etc, when I go to send a check in message and my SPOT is missing/damaged/out of power. Do I not check in? Do I put myself at real risk moving in dark/weather/off trail to get to where I can use a cell phone?
We have agreed that she is to do nothing for X hours based on how far I am packed in + a grace time since I may not have even noticed a problem w/ the device. All this is part of the price I pay of having someone wonderful enough to worry about me at home and I gladly pay it.
One lesson I learned was to keep the little instruction card with my hunting license. Last Sept I was trying to optimize battery life and was sending a ok message then turning the SPOT off. None of them went through because you are supposed to leave it on for 15-30 minutes to fully connect. 2 days later I had cell signal and boy was she pissed and worried.. had already been on the phone with the sheriffs office! Glad I called! Had I reviewed the instructions things would have been fine.. I have to wonder how many people on the REI reviews made similar errors and don't own up to them.
