little_me :
99% if bluetooth adapters are receivers, not transmitters.
99.9% of said adapters assume they get their power through USB
100% of USB headsets want power through USB
100% of USB headsets need to be attached to computer so that their inbuilt soundcard can actually work.
where would your power come from? separate USB battery bank?
where would your headsets drivers come from?
in short.. nope, not going to work, at least in my opinion.
If you do a quick search online, you will find lots of Bluetooth transmitter/ receivers, (I had done quite a number of searches before I even asked the question).
A lot of these have batteries.
The ones I looked at lasted for 10 hours or more - if I could get a minimum of 5 to 6 hours use, I would be happy.
So those two problems are solved.
Another quick search brings up tons of Bluetooth receivers and a lot of these also have batteries (some have AC adapters for static devices like TV's and speakers.
These come with RCA, 3.5mm and Toslink adapters.
As far as I am aware, fibre optic is a digital signal, so they are capable of dealing with digital signals.
So that problem is solved.
Here is one example from Amazon -
https
/www.amazon.co.uk/d/c0d/Golvery-Bluetooth-Receiver-Wireless-Reveiver-Adapter-Streaming/B01KZ1S46A/ref=pd_vtph_107_lp_t_3?_encoding=UTF8&psc=1&refRID=DZQP6BDJVF3M5NJ71RZK
Here is another -
https
/www.amazon.co.uk/Bluetooth-Transmitter-Receiver-TaoTronics-Wireless/dp/B06WD8Z21S/ref=sr_1_6?ie=UTF8&qid=1499596721&sr=8-6&keywords=HomeSpot+BTADP-128-D+bluetooth+transmitters
Here is another which mentions use with wired headphones -
https
/www.amazon.co.uk/d/c0d/Golvery-Bluetooth-Receiver-Wireless-Reveiver-Adapter-Streaming/B01KZ1S46A/ref=pd_vtph_107_lp_t_3?_encoding=UTF8&psc=1&refRID=DZQP6BDJVF3M5NJ71RZK
It appears to me that the tech has been developed, but never applied (or that I can see) to this sort of situation.
I am looking for something along these lines, but with a USB instead of just 3.5mm, RCA, or Toslink.
At least then I could use it wireless with my PC (I did say phone, et cetera in my question)
OF NOTE - I did see that the RX/TX Bluetooth adapters have a RX/TX switch. If this is all they have, OK it is a pain, but still fine. Maybe there is a system out there which is capable of simultaneous signals.