Just add a few drops of water whenever you need emergency light. Never be in the dark again.

This prototype device is made from a gutted arc lighter/flashlight combo. I took out the rechargeable battery and zip-tied a custom-built alum/pyrite/sodium borate copper/magnesium wet crystal cell to it and added a new small switch. On the inside is a small DC step-up oscillator circuit  attached to an ultrabright white LED and a 100uf capacitor as a constantly charging power buffer. The cell produces about 1.5v but lights a 3.3v LED with the special circuit.

When a few drops of water is added to the inlet ports on top of the cell, the electrolyte reactivates and you have power again. It will even activate with the moisture from your breath–! the device will work until the magnesium core is consumed after many, many uses. After activation it will continue to work for many hours and can always be turned on or off via the switch. It is bright enough to be useful and you never ever need to plug it in or buy batteries. Putting crystal cells to work!