The Wiicane by Touch Graphics: "a system for promoting proper use of the long cane in orientation and mobility training for young children and others. WiiCane uses Wii motion tracking technology to provide real-time feedback as users walk up and down a 30' long indoor course. By practicing with WiiCane, some users may learn to walk straight without veering, potentially leading to safer independent travel."
Here's a news clip with in-use footage:
via Peter Meijer, SeeingWithSound