Researchers at Melbourne, Australia's RMIT University devised these bizarre "third arm" chest-mounted"robots to experiment with what they call "playful eating." For science. Video below. From RMIT University's Exertion Games Lab:
In this experience, all three arms (the person's own two arms and the "third" arm, the robotic arm) are used for feeding oneself and the other person. The robotic arm (third arm) is attached to the body via a vest. We playfully subverted the functioning of the robotic arm so that its final movements (once it has picked up the food), i.e. whether to feed the wearer or the partner, are guided by the facial expressions of the dining partner…
Mapping of the partner's "more positive" facial expression to the feeding of food to the partner (via the wearer's third arm) we hoped would elicit joy, laughter, and a sense of sharing based on the knowledge of feeding one another that is associated with positive emotions, however, this could also result in the perception of a loss of agency over what one eats. Through to-and-fro ambiguous movements of the third arm in the air (when sensing a "neutral" facial expression of the dining partner), it gave an opportunity to the diners to express their reactions more vividly, as we know that facial expressions become a key element to engage with a partner while eating.
More at IEEE Spectrum: "Feed Your Friends With Autonomous Chest-Mounted Robot Arms"