Flag down rescuers
Flash your light in groups of three to indicate distress. If you’re in a wooded area, tie the headlamp to the end of a long stick to reach over vegetation. Wave it to create a visible arc. Out of battery? Tap lightly around the side of the lamp with a sharp rock to separate the silver cup behind the bulb. Use the cup to reflect sunlight.
If your batteries die or you can’t ignore your hunger, repurpose reflective elements to attract fish. Work loose the silver LED backing by pressing the edge of the disc with a sharp rock. Then smash the headlamp casing and fashion a gorge hook (pictured) from a shard of sharpened plastic. Braid thread from the headband for a serviceable fishing line. Rather keep your lamp intact? Though illegal in some states under normal circumstances, holding a light over the water at night will attract plenty of species and lure them to a waiting hook or net.
Start a fire
Strip and splice wires from the guts of the lamp until you can touch the ends to either terminus of a AA or AAA battery. (Partial charge will do.) This shorts the battery, turning the wire red-hot with electrical current. Use it to ignite tinder, but beware: Shorted batteries are prone to small but sudden explosions. Wear gloves and glasses if you can.
The lamp’s plastic casing is just a little whittling away from becoming a sturdy needle. Break it open with a rock and use a knife to hone splinters into sewing tools. Use your needle to work loose nylon strands from the headband to use as thread.
The elastic headband can double as a compression bandage or hold a splint in place.