This seems like an area rife for a scam, like hurricane insurance or earthquake insurance. You pocket the money, and when disaster strikes, who is going to sue you when you do nothing? If there was a real bunker-worthy event then all your insurees have been devoured by zombies or dissolved by radioactive strings or whatever.
Historically, savings accounts do much worse than the stock market. People are spoiled from the last decade and don't remember what corrections or bear periods look like. Over time you get 4% over inflation. That's it.