A surveillance device, or surveillance camera, is a piece of technology used to visually record events happening in a specific area.
Chief of security Odo had several monitors in his security office aboard Deep Space 9 which recorded images from the levels and sections aboard the station. This included cameras on the exterior section of the station. (DS9: "Dax")
In 2370, Commander Benjamin Sisko had all of the surveillance cameras on Deep Space 9 sabotaged in order to assist the senior staff in retaking the station from General Krmi's forces, during the Bajoran coup d'état. (DS9: "The Siege")
That same year, the security cameras in the science laboratory on Deep Space 9 shorted out for 43 seconds when Odo was metamorphosing out-of-control due to contamination with a gas that was toxic to him. (DS9: "The Alternate")
In 2371, after being surgically altered to resemble a Cardassian, Major Kira Nerys searched the house of Tekeny Ghemor for surveillance devices. He later stated they were present but only turned on at his request. (DS9: "Second Skin")
Later that year, Constable Odo placed a surveillance device in the corridor of section 47, level 2 on Deep Space 9 in an effort to discover who was planning on placing a weapon in one of the bulkheads there. (DS9: "Visionary")