https://arstechnica.com/science/2017/08/fitbit-for-the-blind-echolocation-based-smartwatch-aids-sightless-steps/

As some Fitbit wearers find amusing ways to skip steps—attaching the devices to hamster balls, ceiling fans, and power tools—a new wrist gadget aims to make sure others never miss one.

The Sunu band smartwatch, designed for people with visual impairments, uses a sonar sensor to detect objects and people within a 15-foot range. When it does, it gently vibrates to alert the wearer, changing intensity as an object or person gets closer. Wearers can also customize it using an iPhone app via Bluetooth, adjusting for walking speed and to make buzzes stronger or weaker.