Many years ago, I was listening to some music late at night, wearing headphones with a curly wire, and I remember thinking "if only there was something you could plug into the jack plug socket which would transmit the sound to a receiver in the headphones, so you didn't need the wire?"
This was in about 1983/4, and I was doing my A levels at the time, one of which was in Design (Technology). Part of that was a project to design and build something, so I outlined my idea to one of the teachers who were taking the subject, and I outlined my idea, and said you could maintain the stereo sound using a VHF frequency, etc etc etc...
I got laughed at. So, I moved onto something else.
A few years after that, the first cordless headphones came out. They mainly used infrared signals, but the highest end ones used... VHF.
To be honest, the electronics would have been well beyond me, and probably the school's budget. Ah, well.