Munzee is a real world scavenger hunt game where items are found in the real world and captured using your smartphone. You then level up and gain rank based on your score. Points are obtained by capturing other people’s munzees or when your deployed munzees are captured by someone else. Munzee is based off of the fundamentals of geocaching and adds another layer of fun to the hunt. Badges can be earned by unlocking specific achievements. — http://www.munz.ee/
So far it’s has been pretty good fun.