The obvious next step is to use this sort of design to keep the bipolar and schizophrenics on their meds. I don't know the legal details, but suspect that the rules might be modified if there were some track record of success. And if the rules are modified with our legislators' customary brilliance, then things would start to get messy: for ADD, maybe? I can't wait to see what'll be in DSM-6... Of course the devil is in the details--in particular in the volume of medicine required. Insulin pumps need to be recharged regularly, I hear.
The programmable feature is dangerous, but I can imagine that fixed dosages might be a problem too--illness and medication interactions. For some people I suppose it is probably worth the risks, but I've no experience. I can imagine somebody trying to gouge out implants.