This is the open-source myoelectric prosthetic hand, Tact.
This project was developed by Patrick Slade through the Bretl Research Lab at UIUC. It consists of a myoelectric prosthetic hand design that can be easily rapid prototyped with 3D printers and common mechanical components. This allows it to be produced as a complete myoelectric system for less than $250.
For complete parts lists and assembly instructions see the assembly pdf file.