Cellphones
This one is best for teams, but you could do it individually
This is for outside
This a scavenger hunt but it doesn't really work unless every team has a reliable cellphone. Have a list of things that you want teams to find and give them all the first one at the same time, they will all run off and have to text you a picture of the thing. If it's correct you can then text them the next thing to find, and so on. First team to find all the things wins.
Scoring is, as always, completely arbitrary, you can award only the winning or award points on a sliding scale from first to last. Decide how you wish based on the number of players.
I will usually require that the photos they send have one of the team (or a part of one of them) in the photo, so they can't just google the thing and send that to me.
Pick things that are fairly easy, you don't want them to get frustrated, think about what can be found in the area at that time of year. Some examples would be: specific flower, dog, ant, a handstand with a red car in the background, someone blowing dandelion seeds, lawnmower, you get the idea.
If you can have someone help manage the teams this one goes easier for you, the texts may start coming in thick and fast depending on the number of teams and you have to make sure you are sending the right thing to the right group.
The very last picture is usually of me holding something specific, and I go hide somewhere not impossible to find. When they find do find me I won't be holding anything, so they have to go find that.