AcousticKitty

Acoustic Kitty was a CIA project launched by the Directorate of Science & Technology in the 1960s attempting to use cats in spy missions, intended to spy on the Kremlin and Soviet embassies, recording the links between the buildings in the area.

A battery and a microphone were implanted into a cat and an antenna into its tail. This would allow the cats to innocuously record and transmit sound from their surroundings.
Surgical and training expenses are thought to have amounted to over $25 million.

The first Acoustic Kitty mission was to eavesdrop on two men in a park outside the Soviet compound on Wisconsin Avenue in Washington, D.C. The cat was released nearby, but was hit and killed by a taxi almost immediately.

Shortly thereafter the project was considered a failure and declared to be a total loss. The project was cancelled in 1967.