There are hundreds of people who for various reasons are tied to the seats for their own safety, as is the case with old people with Alzheimer.
In most cases harnesses or belts are used that impede the mobility of the person no matter how many hours they will be seated.
It would be a good idea to create a harness that allows total comfort and in turn as much mobility as possible.
The idea is to design a harness that only has a hook in the back so that users can not unbutton it by themselves and that is fast and safe. This would be achieved with a similar attachment to the safety belts of the cars with a certain measure to avoid that the users can get up. But allow full mobility when seated.