I don't have an answer to your problem, and know nothing about creating drivers. Although I know that you can only connect(!) to one device. BT goes 1<->1. BUT... Something just hit me. Since many devices can "discover" an active bluetooth device at the same time, the active device must "broadcast" some kind of signal. Then, wouldn't it be possible for the active device just to "broadcast", let us say audio, and for other devices just to "discover" the stream. Without being connected/paired. When searching for a device, that's what's happening right? Since it can broadcast a "visibility" signal, you should be able to broadcast anything. Then, the limitation is in the BT headphones, not being able to catch the stream without being connected/paired.
Instead of going: 1<->1
you go 1->many with the "broadcast" ability??
Of course, this could only be done one way, like with audio->headphones, since a device can't recieve BT streams from many.
Is this an idea, or am I just dreaming??
Anyone more into BT, You tell me...