Drones are already being used for search and rescue missions. Not all of them can fly through narrow holes though. University of Zurich and EPFL researchers have come up with a drone that changes shape to be able to fly through narrow holes. It consists of a frame with 4 rotating arms that fold around it.
The drone retracts its propeller arms and makes itself small to fit through narrow spaces. Once the drone passes through the gaps, it goes back to its previous shape.