Sonic wear design studio have developed a ballet shoe and wrist band that provides real-time feedback to control sound during a performance.
The combination of the two were shown during a dance performance as part of Digifest Toronto
The shoe appears to have a force sensor coupled with an Xbee radio. Rather than try and hide the electronics they make a feature of it with a red band, which I think works well. The wrist band responds to movement so probably has an accelerometer and/or gyro, coupled again with an Xbee.
