Geocaching

A Fun sport which may be handy in the future, for those who are physically able, or know someone who is.  It combines map knowledge with hide and seek, normally using a GPS device, or a smart phone with map capabilities.  Of course, in the future, someone could just tell you the location, and the search would be a lot easier.

http://www.geocaching.com/

The hidden object could be a buried waterproof container, such as a waterproof tupperware-type container large enough to store some food or ammo; or it could be something hidden in plain sight, just large enough for a message:

What looks like a rusty bolt on a metal signpost, is really a hollow magnetic container.

And a fake conduit outside a shed is large enough to hold a spare key to the shed.