Not sure of what your asking in regards to you are stumped on how to work it into the Scout requirements or where, but here are a few ideas you might want to consider.
1. You could incorporate some of the Hiking Merit Badge requirements into the hike for the cache.
2. Let it not rely on the GPS as much as map and compass skills required in Second Class Scout requirements 1 a-b.
3. Include it for a troop or patrol activity (which ranks require a min. number of those activities to advance)
4. If your looking to make it scout related add the troop number or patrol name on the cache, fill it with scout related items (extra badges, pocket knife, compass, etc.)
Hope that helps.