Every person's body has its own bone density, muscle mass, blood volume, and water content. The device, called Touché, sends a series of harmless currents through a user's body. Physiological differences produce differences in the body's impedance of that current. Touché measures this unique capacitive signature. Scientists could apply capacitive fingerprinting to any touchscreen, or to other ubiquitous objects, such as doorknobs and furniture, turning the world into an interactive device. Touché is still in development, and plans for commercialization, alas, are top secret.