Cyalume SnapLight Glow Sticks
I've always carried a couple glow sticks in my pack when hiking and camping for emergency lighting and yet these versatile items never really get any respect when it comes to gear discussion.
My daughter uses them as a nightlight when we're out camping and the comfort it provides her allows her to fall right to sleep and I, by extension, get more sleep.
There's no battery to fail in them so they should work whenever you need them so long as they're not long past their expiration dates. Even then, I've yet to have one fail on me when I needed it and I've used some old ones.
At less than $1 a stick they're not terribly expensive but I still wouldn't run them every night unless Laura demanded it.
They're fully waterproof, non-temperature-sensitive, and provide safe lighting in situations where other methods might provide ignition (i.e. gas leaks.)
Attach a piece of cordage to the end of a glow stick and you can swing it in a circle providing an excellent signal to ground and air searchers should you get lost. The perfect circle, especially one that glows, is not found in nature and will stand out to rescuers.
I recently read an interesting idea related to carrying the sticks. Wrap the foil wrapper with one or two rubber bands and when you need to use the sticks you can wrap the rubber bands around the activated stick and mount it on a tree, stick, or some other object to mark a trail or otherwise provide a visual signal.
My kids each get a glow stick each Halloween as a necklace which makes it easy for me to track them and for cars to see them as they run from house to house. This is one good way to cycle old stock too.
A half-dozen glow sticks in my car can replace flares if I find myself in distress on the side of the road and cleanup is extremely simple when rescue arrives.
Just some ideas for you to ponder.
Thanks for reading,