“You never know.”

A philosophical truism Boy Scouts live by.

It’s why you carry a pocketknife at all times. Band-Aids. Emergency flasks of bourbon.

It’s also why you need this: the FireStar Fire Piston, a metallic device that fits in your pocket and uses compressed air to commence a small inferno, available online now.

Picture one of those baton things that self-defense enthusiasts of the mid-’90s seemed to always carry. Only sans keys. And sans the Steven Seagal–esque ponytails of its owners. That’s this.

Now, imagine you’re out in the woods somewhere and craving toasted marshmallows. You’ll pull this out. Unscrew the igniter side. Pump a little compressed air into the base. Somehow, this’ll produce a single, hot-burning ember that you can drop into a pile of whatever flammables you’ve rounded up. Boom: you’ve got a bonfire.

And if you can’t find any suitable kindling, don’t worry: they’ve included some twine to accelerate the fire-starting process.

This could really come in handy when cabs are scarce after hours in Brookline.