Enchant hand controlled by an opponent
(Target a(n) hand controlled by an opponent as you cast this. This card enters the battlefield attached to that hand controlled by an opponent.)
As Volrath's Motion Sensor enters the battlefield, the controller of enchanted hand balances Volrath's Motion Sensor on the back of that hand.
When Volrath's Motion Sensor falls off the enchanted hand, sacrifice Volrath's Motion Sensor and the controller of that hand loses 3 life.