Ossur's sensor-linked limbs, meanwhile, have stood up to the abuses of everyday activity in Iceland and England (where Olafsson now lives). During the 14-month testing period, the company's two “first-in-man” subjects have worn the devices as their sole prostheses. Ossur checks the equipment and collects data, but the limbs are theirs. And the surgery to implant the sensors was minimal. According to Thorvaldur Ingvarsson, an orthopedic surgeon and head of R&D at Ossur, the procedure took 15 minutes, and each sensor required a single-centimeter-long incision. The tiny sensors (3 millimeters-by-80 millimeters) are powered by magnetic coils embedded in the socket -- the cushioned, hollow component that fits over a user's residual limb, and connects to the prosthesis. Since there are no integrated batteries to deal with, there's no need to replace the sensors (unless they fail for other reasons). “We believe this is a lifelong sensor,” says Ingvarsson.