Safe chemical reactions to start a campfire
Small magnesium metal bars are available commercially, packed with a little iron rod for starting fires. You smack the magnesium with the iron rod and get some sparks. If you have some light fluffy kindling, you are supposed to be able to get a fire going. I suppose a little steel wool would help.
If you soak some cotton balls with KNO$_3$, dry them completely and carry them in a sealed plastic bag, they would make excellent kindling.