Cats are perfect spies. They're small, they're stealthy, and they excel at seducing humans, who can't help but pet them while blathering on about state secrets. This is exactly why the CIA decided to implant listening devices into cats and train them to go where they were told. This is no joke, it's Project Acoustic Kitty.
The CIA chose a grey and white adult female cat to be its first agent under Project Acoustic Kitty. Rigging the cat to record audio was the easy part of the program: a 3/4 inch transmitter was embedded in its skull, with a microphone hidden in its ear canal. The antenna ran all the way along the cat's back to its tail, underneath the fur. Short battery life meant that the cat couldn't spend too long on any one mission, but as it turned out, that was one of the least limiting factors of the whole business.
As you might expect, training the cat to do as she was told was not an easy task. While it was possible to get her to move in a specific direction or go to a specific location in a structured indoor environment, once they brought her outside, she was hopeless. That is to say, she did exactly what her trainers wanted, unless she got bored. Or distracted. Or hungry. And, being a cat, she was at least one (if not more) of those things a large portion of the time.
Apparently, her hunger issues were somehow "addressed with another operation," and her training was intensified until the CIA was reasonably confident (or however confident they could possibly be) that the cat was capable of actually going where she was told. All told, the program had taken about $20 million and five years, but Acoustic Kitty was finally ready for deployment.
The first mission took place in a park near the Soviet embassy, where the cat was tasked with eavesdropping on two men. A CIA reconnaissance van across the street released the operative, who took a few steps towards her foes and was immediately run over by a taxi.
This was pretty much the end for Project Acoustic Kitty, as the CIA concluded that "it would not be practical." This is not to say that no advances were made, however: the CIA discovered (through, one has to assume, a stupendous amount of effort) that cats "can indeed be trained to move short distances." And all it took was five years and $20 million.
You can read more about Project Acoustic Kitty and other CIA projects in the book Spycraft.
Via Mental Floss