Although spy cameras are chiefly used to detect robbery or similar activities, when people mount their spy cameras on their office's main gates or in porches of their houses; but with time there has been discovered many great purposes to use spy cameras for. It wasn't too late until the realization that robbery or stealing is not the only 'event' that needs to be caught. Certain other things take place which if recorded, could be feasible evidence in the footage.
However, it's to be noticed that the spy cameras can't be by our side all along; and it's not only on the outside of a building where events that are worth recording happen. For that, technology has been advanced enough to have introduced the most portable spy pen cameras.