As I recall, it uses a combination of sound and vibration to advise the user of objects. It, unlike other ETAs, detects drop-offs. Guide Dogs in Australia were developing the Pathfinder several years ago. Its inventor, Dr Tony Heyes, then worked for them. It is a head band aid.
Musical notes run down a scale as the user approaches an object.
The distance between notes was, if I am correct, about 15cm or six inches. That is, distance measurement is not continuously variable and, rather, is in steps. The shortest range is, I recall, rather more than half a metre - more than two feet. That is, anything at that distance or closer gives the same note. I used the Pathfinder only briefly.