The Sunu wristband uses a high-frequency signal to bounce off nearby objects and detect their distance, and then it vibrates to tell the wearer about them. This gives vision-impaired people an opportunity to perceive their environment in a new way. At this stage, it's pretty crude, but it does work and will probably work for more people than click-sonar does. (Yes, there are humans who can do that, just not many.) So if you are vision-impaired and good at interpreting tactile signals, this might be something to investigate.