Pigeon photography was an aerial photography technique invented in 1907 by the German apothecary Julius Neubronner, who also used pigeons to deliver medications. A homing pigeon was fitted with an aluminum breast harness to which a lightweight time-delayed miniature camera could be attached.
He publicized the technique at the 1909 Dresden International Photographic Exhibition. The lack of military or commercial interest in the technology after the First World War led Neubronner to abandon his experiments, but his idea was briefly resurrected in the 1930s by a Swiss clockmaker, and reportedly also by the German and French militaries and the American Central Intelligence Agency.
(via Everlasting Blort)