Want something like Geocaching for a group? Start with what you want to do together: look for hidden containers, complete missions, or find a hiding team of friends.
Geocaching
Geocaching lets you follow coordinates to hidden containers and sign a logbook. Your group can choose a route and look for caches together.
Team missions
Goosechase lets an organizer create missions for participants. It's an option if you want to write the tasks for your own event.
Hide and seek with Near
I made Near for friends who want to play hide and seek across a city. One team hides and stays together; seekers use Radar, Thermometer and other questions to narrow down the map. Answers shade the areas that are ruled out.
Choose a border, agree on the rules and join a private room. The home game setup guide walks through it, or you can open Near.