I'll preface this by stating that I know Sonos headphones has been requested from time to time, and it's probably never going to happen. I'd also say that the particular idea I have in mind doesn't exactly in Sonos wheelhouse. But it's an idea, and I feel like sharing for the hell of it.
So, I went to the gym the other day (first time in a long time) and put earplugs in like usually, and like what 90% of everyone else is doing. I thought about my 14 year old son will likely start coming to the gym with me a few months from now. I'm looking forward to that, but a part of me was also thinking that I won't be able to put the earplugs in and communicate with him at the same time.
But does that really have to be the case? What if there were headsets available that came in sets where each person with the headset could listen to streaming music of their choice (or off their phone) but have an open communication line with another person or group also wearing the headphones. So for the gym example, I could be listening to the old man music I need to motivate me, my son could listen to modern crap, and we could still talk to each other without having to pull the earbuds out.
And this really isn't groundbreaking tech either. Isn't this exactly what happens with online gaming? In online gaming, the headset will play the audio of the game, overlaid with the communication from others in the party you're currently in. I'm just suggesting that the communication be done without a server in between, over Bluetooth or wifi depending on the particular scenario.
The use cases go well beyond my gym example, as it works in any scenario where a person wants be isolated in audio, yet open to communication to a group of people. A group of runners or some other athletic activity. A family on a road trip where everyone wants to listen to something different. A group visiting a tourist site or similar excursion where they may split up briefly but want to remain in contact. A couple who want to communicate while in different rooms in the house. A family where one of the members wants to use headphones for the TV, yet not feel isolated from everyone else.
In terms of Sonos, the headsets could fit as speakers within the a Sonos setup, but limiting it to just the local wifi would be a big drawback. Although the greater range of wifi over Bluetooth communication woud be a big plus where it's available. And technically, all the hardware you'd really need is already available with your phone the earplugs that came with it. Lastly, I have no idea whether the communication could work well enough in a mobile setting to be reliable.