My uncle in the US actually worked on a study that was for some section of the US Govt penal system about 10 years ago now, his side of it was working on making the devices small enough and last long enough but apparently they had issues with another side of the project which was making it in a place that was impossible to be removed (from memory they were wanting to bind it to the spinal cord or btwn joints in the neck, that wasnt his section - not sure if it was to hard / to expensive or they realised that no govt would let that crazy **** pass). It was planned to be only on prisoners that wanted it and it would reduce their sentance to free up some jail space. Could prob fine more info if i talked to him about it though