Reverse Geocaching?

Geocaching is a really cool hobby where somebody hides a container, sometimes so small it only fits a tiny bit of paper for a log all the way up to ammo cans (sometimes larger). They then post the coordinates of the container on a geocaching website where other people then try to find it.
One would think a hobby using GPS like that would be easy, but it can be a real challenge.
Anyhow, there is a new take on it called Reverse Geocaching. In this case you are given the cache up front, but it has a special device on it to keep it from opening until it is in the correct location.