Copy paste from this VirtualWorldlets article :

The StringWalker is the work of Hiroo Iwata from the University of Tsukuba and will be demonstrated for the first time outside Japan at SIGGRAPH.

The walker works by means of eight strings – hence the name – that are actuated by motor-pulley mechanisms mounted on a turntable.

It works, basically, by using the strings to measure the direction and force of the step. The distance and trajectory of that movement is calculated based upon the direction and length of string that has passed over the pulleys. This is then used to work out the force of movement, so the device knows how much to push back against the user, to prevent them actually moving.

StringWalker will be displayed at the upcoming SIGGRAPH conference 5-9 August 2007 at the San Diego Convention Centre in San Diego, California, USA.

I’m not sure I understand how you get “pushed back” by the strings. Are you gliding on the surface?

Related article : VR Shoes (also from Tsukuba University)