Mini cams and pen cams are other widely used types of spy cams that are mostly used by secret agents and detectives for covert surveillance & sting operation. These small and discreet devices can be carried anywhere and everywhere without any hassles. A spy camera is powered by a 9-volt battery rechargeable battery, which assures long and uninterrupted functionality. There are countless venues especially online shops, from where individuals can avail varied spy devices at most reasonable rates.