In the past few years, we have covered a bunch of third arm projects that can help the wearers get more done while having their hands free. Christian I. Penaloza and Shuichi Nishio have published a paper that explores the idea of using a brain controlled robotic arm to make users more productive.
This approach allows you to do things not easily possible with two hands. For instance, you can use something like this to continue typing on your keyboard and have the robotic hand give you some water. More information about this study is available here.