My google-fu is failing me because all I'm getting is blogspam, but I could have swore that some higher-end washing machines had a feature where when they broke down, they would emit some kind of diagnostic noise. Not just the standard series of beeps, but complex digital data. When you called in for warranty support or repair, they would guide you though pushing some buttons on the machine, the machine makes the noise, it goes through the phone, and the call center person on the other end could decode it. Or a repair tech on-prem could presumably decode it with an app on their phone.

Also, ham radio operators are doing some amazing things with audio-encoded data. You can send a message halfway around the world with just a few watts and a person with a computer on the other end can received and decode it, even if the signal itself is _below the noise floor_. Of course, the tradeoff is time: it takes a few minutes to transmit the small amount of data required to make a contact.