kbd-audio

ggerganov/kbd-audio is probably the best-known one. The amusing aspect is that this is so easy that multiple good ways someone could hobby program this long before AI was a thing. The sound of a bunch of keypresses may just blur together to our human ears, but if you try, you can tell that different keys make different noises, which is really the key insight. Between the different noises, the possible directionality you can get from a stereo (or more) pickup, and characteristic delay patterns during typing various bi-grams, there's a ton of information leakage in a recording of a keyboard.