Conventionally, motion capture makes use of reflective dots or small LEDs attached at key points on a person's torso, limbs and head. Capturing the movements of these points using an array of cameras allows animators to create a computerized skeleton, which can then guide the movements of an animated character, for example.
Several sensors measuring about 2.5 centimetres on each side are attached to a person's legs and arms. The sensors detect movement in two different ways: accelerometers and gyroscopes measure motion, but ultrasonic beeps are also emitted.
Tiny microphones mounted on the torso pick up these beeps, allowing a laptop computer, carried in a backpack, to calculate the distance to the sensor. The system is similar to, albeit much simpler than, bats' ultrasonic echolocation, and together with the motion sensors provides a more accurate overall picture of body movement.
Read in full - 'Cheap sensors could capture your every move'