Repurposing a dead spider to build an actuator
onlinelibrary.wiley.com
onlinelibrary.wiley.com
For a work straddling the boundary between advanced science/engineering and Lovecraftian horror and for coining the world "Necrobotics". Also, they should get an Ig Nobel as a warning to discourage other scientists from venturing too far in that direction...
More likely if such a technology were ever applied to humans, it would be to allow paralyzed people and others with irreparable nerve damage to use their bodies.
In a punitive justice system that would probably be considered a feature. There's already labour which is largely pointless, better done by machines, and harsh on the human body, but still used in prisons. E.g. I believe the nearest prison to me does light metalworking, concrete work (making paving tiles, flower pots, etc.) and other simple things that would probably be a lot more cost-effective to automate if the workers were being paid more than a few dollars per day.
If you can get the same work done with near-mechanical consistency, and also compel prisoners who would otherwise refuse to work and not have to worry about them taking unauthorised breaks / stealing tools or materials for improvised weapons / attempting to escape, why wouldn't you use it?
There's also plenty of other nightmare scenarios such as puppeting people for sex work, suicide bombings, etc... I'm sure there would be plenty of medical / assistive tech use cases for such a technology but the potential for abuse is huge, and that's where the horror comes from.
And this doesn't change the fact that all the expensive parts of automation remain for this case - the moment you stop controlling the human body with a human brain, you need to program every individual bodily movement. You still need to provide food, water, rest, and medical care to these people or their bodies will stop working. Biological variation means you don't get near-mechanical consistency, and odds are the expensive programming work you did isn't even transferrable between different bodies. In fact, normal fluctuations in fatigue and adrenaline and bodily changes like increase in muscle mass mean your program may need modification from one day to the next. By comparison, robots are cheap, strong, and reliable.
Yes, you get the benefit of restricting people's freedom of movement, but you know you can also do that with a straight jacket, or holding a gun to their head. The same goes for sex workers and suicide bombers and anyone else you would seek to control against their will - if you have the means to force a puppetting device on them, you almost certainly already have the means to force them to do anything else you might want.
Maybe if you took the technology far enough that someone could be almost instantaneously puppetted via a non-invasive procedure and the equipment was small enough that no one could tell the person was puppetted you could have some real issues with the ultimate identity theft, but I imagine by that point technologies both to prevent oneself from being puppetted against their will and means of detecting those who are being controlled would be available.