A sensor web was a garment of finely-woven SONAR units, typically utilized by the blind during the 23rd century to help carry out normal lives. The web could be worn naturally over everyday clothing. It emitted low-level SONAR scans undetectable to the Human senses (presumably ultrasonic), and translated return signals into media perceptible by the trained wearer.
The blind Dr. Miranda Jones was one user of a sensor web in 2268. She stated to Captain James T. Kirk that she could "play tennis" with him while wearing the web. (TOS: "Is There in Truth No Beauty?")