I'm working on a geocache (http://www.geocaching.com) that consists of a series of switches that have to be set in a certain order (a simple binary puzzle) to release a spring-loaded drawer. As this will be in place for a few "Years", I was thinking along the lines of an automotive battery charger solar panel to charge up a capacitor to power something like a trunk release that holds the drawer in place. I was thinking about a rechargeable battery system, but concerns were raised with life of batteries, Leakage, replacing batteries, etc. The idea here is to place and don't worry about for at least five years.
Any thoughts or ideas are welcome. The further outside the box, the better.