From secret CIA files declassified in 2001, as written up in the Guardian
In another snapshot of folly offered by the new files, a memo dated 1967 on "Views of Trained Cats" looks into the possibility of surgically inserting microphones and transmitters into cats and using them as walking bugs. The operation was codenamed "Acoustic Kitty" and was a resounding failure.
Having wired their first trained cat for sound, they released it near a park with strict orders to eavesdrop on two men on a bench, but the poor animal was run over by a taxi before it had taken more than a few steps towards its target.
The CIA researchers came to the conclusion that they could train cats to move short distances, but that "the environmental and security factors in using this technique in a real foreign situation force us to conclude that for our (intelligence) purposes, it would not be practical."
[Hat tip to Nolo
in the comments to this sad story
about the use, frankly, of pig-torture to train medics shipping out to Iraq.]