Nearly eight years ago, DARPA, the US Defense Departments advanced research agency, set out to find a better solution for amputees than the metal hooks still widely used today. Now, the Food and Drug Administration (FDA) has granted its approval to one of the projects that came from that effort: a mind-controlled prosthetic limb called the DEKA Arm. A number of other scientists and engineers around the world are working on similar devices, but this is the first such prosthetic to get FDA approval. The prosthetic device comes from a company founded by Segway inventor Dean Kamen, and it is roughly the size and weight of an adult arm.