Fernando Albertorio is legally blind, which can make it tricky to navigate busy sidewalks without bumping into things. He’s got a sort of superpower to help him, though: he can sense objects—people, doorways, trash cans, lamp posts—well before he touches them.

Albertorio, cofounder of a company called Sunu, doesn’t actually have a sixth sense that alerts him to obstacles in his path. But he does have a wrist-worn gadget he and two cofounders developed, which uses a sonar sensor and subtle vibrations to do exactly that.

The band, which he wears daily, emits a high-frequency ultrasound wave that bounces off objects he encounters. The band considers the strength of this reflection and produces a vibration that’s stronger or weaker depending on how close or far away the object is.

“I feel much more confident moving around these spaces where normally, instead of walking faster, I’d be like, ‘Uh, where am I going?’” Albertorio said earlier this week while traversing the busy streets of downtown Mountain View, California, at lunchtime.

Albertorio and his cofounders, who are currently participating in the startup accelerator Y Combinator, hope their band can be useful to others who are blind or visually impaired. The National Federation of the Blind says there are as many as 10 million such people in the U.S. alone. To get to this market, the startup will begin shipping its $299 Sunu Band to buyers later this month.

Sunu isn’t the first to harness sonar as a navigation aid for those with low vision. Some people use their own voices for echolocation (think of bats), and products are available that do something similar. The startup’s approach is interesting, though, because it’s useful both to people who need help getting around all the time and to those who can see just fine but may need extra assistance in certain situations (while cycling, perhaps).

Albertorio and I went on a walk so he could show me how he uses the Sunu Band. He wore it with its sonar sensor positioned so that when his arm was flat against his side, the sensor pointed in front of him. He had no problem avoiding all kinds of things, from big concrete planters to hanging branches, as we navigated busy sidewalks. He showed me how he could use the band to sense doorways by spotting gaps between vibrations that signified the different sides of the structure. At one point, I leaned over him to push a crosswalk button at an intersection, but he stopped me and did it himself, saying he felt the pole with the button on it as we approached.

He has even hiked with the band, using it to help him sense the edges of the trail. Recently, he ran a 5K race with it.

“It was amazing,” he says. “It was just that feeling of independence when you’re running.”

I tried the Sunu Band out and was surprised by how sensitive and responsive it was to pedestrians, pulsing more urgently as they moved toward me and then more softly as they passed.

The band works with an iPhone app via Bluetooth, letting you adjust the feedback intensity and see the battery life (it lasts about four hours total, he says, but since wearers are likely to turn it on and off, they’re likely to get a day or two of use out of it). Over time, Albertorio says, Sunu plans to let you adjust for things like how fast or slow you walk, and integrate the app with services like Google Maps to help guide the way to specific destinations. He says that the app isn’t necessary for the band to function, however; he knows that not everyone who may want to use it has a smartphone.