RFID tag arrays can be used to track a person's movement

Radio-frequency identification (RFID) tags have become a key component of global commerce, enabling stakeholders to track physical assets quickly and reliably. Deployed properly, the tags could be used in a new class of wearable designed to track physical movement and shape change.
Researchers at Carnegie Mellon University have figured out how RFID tags could be used do things like control virtual avatars or tell slouching users to sit up straight.