A collar that will keep him from leaving the room. The remote would go to Joseph, so Alexi could, in a way, further show his trust. The only setting would be to keep him in the bedroom and bathroom areas, he would not be allowed to leave past those two room. Not a shock collar, but literally he would just freeze in the doorway or window, most likely falling back into to room after a couple seconds. Since the other controls have to be manual implemented, with Joseph going about his chores, he will not be there to enact them, so, in other words, Erik COULD kill Alexi if he wanted to :P