I think it was in the book Spycatcher [0] that I recall there was a story of how English intelligence bugged a foreign embassy with a microphone and was able to figure out what they were typing on a typewriter by analyzing the sound of the keystrokes. That was way back in the 1950's I think, so the idea has been around for a while. The book has a lot of interesting details about spy technology at the time. In addition to all the juicy intelligence stories it's also a fun read from a security engineering point of view. The British government tried to ban it which naturally triggered the Streisand effect and made it a best seller.

[0] https://en.wikipedia.org/wiki/Spycatcher