Scavenger Hunt app that uses map to identify item for the hunt

Would like an app that gives a clue for an item where you have to go hunt in a location to find the item that the app feels is close to that location. Example: Clue is a flower. You open up the map and get a radius of where to find the flower. The radius of where to find the flower gets smaller as you get closer. Once you have the clue you can verify it and if correct it'll unlock the next clue.