Eton makes some pretty cool products for emergencies. The Blackout Buddy H2O happens to be a water activated emergency light that provides you with light for 3 days. This one-time use device is activated by water and does not require any batteries. It has a Magnesium-oxide battery module. You just have to add water once per day to keep the Blackout Buddy H2O going for up to 72 hours.
The Blackout Buddy H2O has a rugged, weather-proof housing and can be stored for up to 10 years. You can use it in any weather condition. The device can even be submerged in water. It has a lightweight and compact design. You can get yours for $9.99 at this time.