It does what Bluetooth headphones do but with regular headphones. More usefully, it is a Bluetooth line-output to plug into an amplifier which is what I am actually working on. This will go into an amplifier that can connect to my laptop and is integrated into my bedside laptop stand (I'm physically disabled so in bed most of the time). I'm working on making several parts of my laptop stand more modular. I want this to be removable to use elsewhere if I want and charged when not in use. It therefore has a use, a place of storage, and is always available.

Looks like it receives audio wirelessly and to the headphones.

It’s the guts of a pair of headphones, retrofitted with a battery and audio jack. Consider it a Bluetooth audio receiver and DAC with standard audio output.

Audio stuff.

Cheapest Chinese Bluetooth headphones from AliEx around 2019. I think it is an AC6905 chip. The toolchain is rather obscure and piecemeal with write-ups on GitHub and eevblog, but that is beyond my interest. This one was too weak to be useful or one of the audio drivers went out or wire was bad. I have a half dozen of these sports ear buds style headphones that have gone bad over the last decade. Even ones that come from the same brand end up having different boards.

From the post, it sounds like it's just whatever they ripped out of an old pair of Bluetooth headphones... So probably a proprietary purpose-built PCB rather than something more generalized like an esp32 or something.

As them out on a date first

IT'S AN AUDIO THING