Other mistake: As Roy meets his daughter, he gets out of his car and we see the car door left open as he runs towards her. Near the end of their conversation, the camera focuses on Roy, and through the space between his body and right arm, you can see the side view mirror indicating the door is now shut without anyone touching it. (00:26:50)
Other mistake: Throughout the movie Roy buys Tareyton cigarettes, but if you watch closely he smokes "Kool" cigarettes, easily identified by the gold label.
Answer: They needed to get the password for Roy's safety deposit box. They planted the camera and microphones so that they could listen in on the conversation and know what the password is.
Casual Person
But he gave the code to the doctor who was in on it.