If today's Pentagon leaders get their way, the next generation of fighter jets, body armor, computer systems, and weapons will understand more about the pilots, soldiers, and analysts using them than those operators understand about the machines they are using. The very experience of flying the plane, analyzing satellite images, even firing a gun could change depending on what the weapon, vehicle, or software detects about the person to whom the weapon is bound. To make this dream real, Pentagon-backed researchers are designing an entirely new generation of wearable health monitors that make Silicon Valley's best consumer fitness gear look quaint. They're discovering how to detect incredibly slight changes in focus, alertness, health, and stress—and to convey those signals to machines. Design the boots well enough and the super soldier will arrive to fill them.