Georgia Tech Professor Gil Weinberg figured drummers needed three arms now-a-days, so he made a mechanical arm so they can have exactly that. It doesn't connect to your brain just yet, but it will! I'm seriously making none of that sentence up, by the way – How Stuff Works has the lowdown on this insanity.
“The biomechatronic device attaches to a drummer’s shoulder to add a third arm that responds to the music and motions around it. The robot drumming device can also improvise as it plays, and future iterations may eventually know its users so well that it can read brain waves to sense where the music is going next … [The arm] features accelerometers that tell the arm how close it is to the drum set and lets it know when to change angles and reach. The arm also recognizes a drummer’s gestures and senses the speed and style of play to respond accordingly.”
Here's the "connect to your brain" bit as well.
“They’re currently tinkering with an electroencephalogram (EEG) headband that reads a user’s brain waves. The idea is to detect patterns that would signal the prosthesis before changes in patter and tempo happen. A successful drumming robot could provide the groundwork for other robotic third-arm helpers with medical, military and construction applications, among others.”