Drones and robots are being used in search & rescue and inspection missions all the time. MIT researchers have come up with an autonomous system for a fleet of drones that enables them to search under dense forest canopies where GPS is unreliable.
Each drone uses laser-range finders for position estimation, localization, and planning. They fly around to create 3D maps of the terrain. An algorithm is used to recognize unexplored areas. Object detection can be used to identify missing hikers.