Abstract: A method and apparatus for monitoring posture are disclosed. A first unit is attached to a first position on a user's body, and a second unit is attached to a second position on the user's body. A signal such as an ultrasonic signal is transmitted by the first unit to the second unit. In response, the second unit transmits a signal back to the first unit. The round-trip travel time of the signals is proportional to the distance between the units. If the distance differs from an ideal distance by more than a maximum allowable amount, improper posture is indicated to the user by an alarm signal.