Sometimes i wish for an organization that can't exist.
A department of keeping track of people.
However, this US Mail like department would have to be completely opaque.
They would deliver a message to the stated person.
As long as that person kept their location information current.
And this department would have to NEVER share this information with law enforcement.
But, since this organization would have to have a database, then it would be hacked and leaked. That is, if the organization didn't have a back door for police officers, etc built in.