Well, here I am, 3 years later, searching the Net for this kind of controllers.
I saw the [Altura MK2+] (Altura MkII+ Theremin MIDI Controller / Arpeggiator - Zeppelin Design Labs) that can act as a theremin as well but it’s not available in Europe and i’m afraid tariffs war going on would not play on my advantage.
Also, it’s a small company and they don’t seem super sure that their product works with every MIDI device.
So that’s it for sensor controllers: Leap motion or any other camera one, the only ring one surviving seems to be the Genki Wave and the one Hymogen Heap uses is at 2700USD.