A cool device. Seems like its completely autonomous. Seeing as we used to have tails in our evolutionary past, I wonder if this could be fitted like a myoelectric prosthesis around the coccyx or something and function like a biological tail.
I'm not sure that I buy that first assumption though. Measuring signals might be possible, and it might be possible to learn how to move the tail based on signals produced during conscious attempt to move the tail. But I don't see how it would be possible to send signals back to the brain.
To get any meaningful spinal communication in this hypothetical scenario, you'd be looking higher up in the sacral region. Unless this hypothetical also includes some magic star trek technology, you'd be invasively implanting electrodes there, which sounds like a fantastic way to trigger fecal incontinence and chronic pain.
I get the fun idea of returning humans to our primate origins, but modern human anatomy has left us effectively nothing to work with. It's an anatomical dead end.
I think the tail attached to the back might be physically awkward or impractical. After all, there's probably a good reason that all animals with prehensile tails have it attached to the pelvis. But then again, it may just be an artifact of it being an extended spine.
Unironically, I think this is a fantastic idea that might actually catch on if/when humans start spending extended time in zero g environments. Tails do have a lot of advantages for navigating and manipulating 3D space.
Unfortunately, I don't think we'll be able to actually solve the problems with this design until we're actually in space regularly.
The final / functional version should be; as it stands though, it's a prototype / concept. It'll need a lot of sensors and fine-tuning to work as intended though.