Rows of motorised measuring tapes record the amount of time that visitors stay in the installation. As a computerised tracking system detects the presence of a person, the closest measuring tape starts to project upwards. When the tape reaches around 3 meters high it crashes and recoils back.
Each hour, the system prints the total number of minutes spent by the sum of all visitors. Commissioned by the Museum of Contemporary Art, Sydney
Source: Rafael Lozano-Hemmer http://lozano-hemmer.com/tape_recorders.php