Pendaphonics is a collaborative research project of Arizona State University, USA and Aalborg University, Denmark.  Pendaphonics uses physical pendulums as interaction  devices, driving multimedia feedback based on the physical motions of the pendulums.  Documentation of the first incarnation of this system can be found here: http://www.pendaphonics.com/.  Pendaphonics is part of an acrobatic dance perfomance by STREB Extreme Action: http://www.streb.org/.  It was installed as an art installation at the New Interfaces for Musical Expression 2009 conference at Carnegie Mellon University.