Different people pointed me at this new Bluetooth Device sold and produced by aircable. They promise that this Bluetooth “Dongle” has up to 30km range. I always thought the theoretically maximum range of Bluetooth is around 3km. Practical approaches extended the range to 1.1 miles, using the BlueSniper Rifle.

Maybe I am wrong, but in my opinion the reason for the theoretical limitation is signal propagation delay. When I have more time I will check the spec.