The theory is that it will shunt off the higher induced voltages, so it will not destroy the electronics. The reality is that their are so many variables (EMP or CME, Proximity, surroundings, etc.) that no one can be sure it will work.

My thoughts are, if I'm away from home and one of these events happen, if this thing works it is priceless and a literally a live saver. If it doesn't, then I'm no worse off than anyone else and the money I spent on it is worthless anyway. Now you could argue that investing the $300 spent on this would be better spent on food, tools, guns, ammo, etc. That would be a valid argument, but everyone has to make choices. I travel a lot, often times being over a 1,000 miles from home, so I think its worth having.