The wire band headset I linked to previously is exactly what you pictured. Though, it doesn't from the get-go mount to the helmet. You would have to bend it and find a way to attach it (tape is what I used).
That doesn't answer the "device" question though - the radio, phone, intercom box, bluetooth box, what ever you want to call it.
A phone in an active call is the closest I can picture to what exists and is customary that you are asking for - but that requires cell towers. You can't link a bluetooth headset to another bluetooth headset - the bluetooth headset is an extension of the device (cell phone), not a stand-alone device.
For what it is worth, I have adapted a bluetooth headset to a bluetooth box for 2-way radio use that allows PTT control. The box I use is a RigBlaster Blue. The down side to the box is that with a bluetooth headset it only does VOX (internal to the RigBlaster, not the radio). Going back to my comments on VOX being a PITA in mobile/high noise environments - the same holds true with the bluetooth headset. So I modified the RigBlaster to run PTT with a Bluetooth headset. See video.
Best of luck on your search.