Pain is an indispensable tool for survival. The prick of a nail underfoot is a warning that protects you from a deep, dirty wound--and maybe tetanus. The sizzle of a steel skillet is a deterrent against a third-degree burn. As much as it sucks, pain, oddly enough, keeps us from hurting ourselves. It's a luxury that prosthetic users don't have.

One of the most advanced prosthetic arms yet is coming to market this year, brought to you by robot-friendly U.S. military agency DARPA and the Segway inventor Dean Kamen. Mobius Bionics LLC, a medical device company, will produce the Luke arm commercially, named for the lifelike replacement Luke Skywalker received at the end of Star Wars Episode V: The Empire Strikes Back. The Defense Advanced Research Projects Agency (DARPA) funded the arm and Dean Kamen's DEKA company designed it, with the goal to "develop an advanced electromechanical prosthetic upper limb with near natural control that would dramatically enhance independence and improve quality of life for amputees," according to the Mobius Bionics press release. The prosthesis combines a number of features to accomplish that goal. The system can accommodate people with varying levels of amputation.