Also I expect the medical device manufacturers will most likely join this market eventually and they have a less-than-stellar record of security with their devices. Some company is going to connect it to the internet and regulation will be too glacially slow to stop it.
Perhaps I wasn’t clear but that technology already exists and is in use. It’s much easier to do prosthetics because you can just hook it up to the nerves on former limb stub.
There isn't a need, but if the same thing happens here that happened everywhere else in the tech industry, there will be a motivation for over-the-air firmware updates. If the average person won't install adblock because they don't realize the end result of ad network tracking, why would they object to a prosthetic that records their every move? Time and time again, the public has shown that they have no practical aversion to being creeped on and abused in ways that don't immediately translate to pain or lost money.
One thing I was surprised to learn recently was that mentally controlled prosthetics are simply machine learning algorithms trained to interpret the electrical signals and produce physical outcomes. In hindsight that seems obvious but before that I had assumed something more complicated. I think a lot of great stuff could come from this. Especially art. Either generating things that the device observes you find enjoyable or generating music you’re mentally composing could be awesome. Imagery could be great.