Things you don’t want to hear in the wilderness with a dead cell phone:

“Oh God, we’re lost.”

“Oh God, I didn’t know an ankle could twist like that.”

“Oh God, we really need to get the football scores.”

Enter fire. And water.

Here’s FlameStower, a handy gadget that powers a USB charger using nothing but those two primal elements, available for preorder now and shipping this fall.

This is the kind of thing that can prevent your next camping excursion from becoming the topic of a Jon Krakauer book.

It’s only eight inches long and weighs half a pound, so it’s easy to add to your backpack. When you need it, just start a fire. Use your camp stove, use a Zippo, use a magnifying glass. Stick it over the fire and dump some water in the other side (if you don’t have any water, well, get creative).

And just like that, the temperature difference between the hot and cold sides creates electricity—about enough for three minutes of talk time for every one minute of charge time.

So you know what to do then.

Yup, order an airdrop of marshmallows.