Acoustic Kitty was a CIA project launched by the Central Intelligence Agency Directorate of Science & Technology, which in the 1960s intended to use cats to spy on the Kremlin and Soviet embassies. In an hour-long procedure a veterinary surgeon implanted a microphone in the cat's ear canal, a small radio transmitter at the base of its skull and a thin wire into its fur ...
source: https://en.wikipedia.org/wiki/Acoustic_Kitty