Students learn about the global treasure hunt called Geocaching in the intro PowerPoint. The project has them build and hide caches on campus, and log their coordinates using several GPS devices that I have gathered through the years (I started with only 1 the first year).
The culmination of the project is to have each class period search for caches hidden by a different class period.
I also encourage students to create and account on geocaching.com, download the Geocaching Ap (available on the Google Play store and also the Apple Ap store), and take their families on a search for real world caches hidden in their part of town. As an alternative to the official Ap, I let students know that they can download the ap called "c:geo", which has all the functionality of the official ap, but is free :)