Make a fire from a phone battery.
If you get lost far away from civilization, your gadget will be useless unless you start a fire from its battery.
Many smartphones and tablets have lithium (Li-ion) batteries. If you pierce such a battery with something sharp, it’ll cause a chemical reaction that results in fire. All you need is to prepare firewood in advance.
so I have a phone, but I'm going to explode it
( and maybe I die, doing it )
instead of calling for help !