Sleeping Beauty

Lucy (Emily Browning) is a university student who holds a number of odd jobs: She volunteers as a test subject at the university medical research lab, works at a coffee shop, and makes photocopies at an office. She also attends a high-class bar, offering herself as a sex partner. Her landlord dislikes her, and she spends her time visiting an aloof man, Birdmann (Ewen Leslie), who is attracted to her, and though she doesn't return the affection, she appears happier with him than at any other time.Lucy responds to an ad and is invited to meet Clara (Rachael Blake), who describes the job: freelance silver service in lingerie. Lucy agrees and Clara tells her that she will never be penetrated during these encounters. Clara says she will call Lucy by the name Sarah. Lucy gets beauty treatments before arriving for the event. She is the only girl dressed in white lingerie; the other women seem much older, have black lingerie, and wear severe makeup. The event is a formal dinner party at an elegant home. Lucy serves drinks for the party and goes home with the money she made from it. After one other session as a serving girl, Lucy gets a call from Clara's assistant Thomas (Eden Falk) for a different request. Lucy is driven to a country mansion, where Clara informs her that she'll drink some tea and then fall into a deep sleep. Lucy is seen lying in a large bed, sedated, as Clara leads in the man who hosted the first dinner party. After Clara reminds the man of the no-penetration rule, he strips, caresses Lucy's body, and cuddles up next to her.Lucy is evicted from her room by her landlords. She instead rents a much more expensive apartment. After two more sleeping sessions at Clara's house, Birdmann calls her; he has overdosed on drugs, and she visits him as he dies. She takes off her shirt and gets in bed with him, sobbing but making no effort to help him. At his funeral, Lucy blandly asks a former acquaintance if he'll marry her. Dumbfounded, he refuses, citing his new relationship, and several character flaws in Lucy.Lucy is fired from her office job and buys a small, concealable camera. She takes drugs with a coworker, goes night-swimming with him, and wakes up naked in her apartment with him. The next morning, she is hung over and late for her assignment with Clara. Once Lucy arrives, she asks Clara if she can see what happens during the sessions while she is asleep. Clara refuses, saying it will put her clients at risk of blackmail. Right after being placed on the bed for the session, however, Lucy awakes and removes the small camera which she had concealed in her mouth. She is able to set the camera and return to bed before being discovered. The client is once again the first man, but this time, he also drinks the tea with a much larger dose of the drug.The morning after, Clara comes in and checks the man's pulse, showing no surprise when he cannot be awakened. She then tries to wake Lucy but is at first unable to do so, eventually having to use mouth-to-mouth resuscitation. Lucy awakes and, discovering that the naked man lying beside her is dead, screams.
The movie ends with the scene captured by the camera that Lucy had installed: the dead old man and the sleeping girl both lying on the bed.

Question: What does Lucy have hidden in her mouth?
Answer: A camera