Researchers at the Rehabilitation Engineering Research Center on Mobile Wireless Technologies for Persons with Disabilities, located at the Georgia Institute of Technologies, are hacking a variety of off-the-shelf components and mobile devices to improve the quality of life for individuals with various impairments. From wearable computers that help the blind navigate to gesture-based interfaces for consumer electronics, "all of our projects are designed to increase a disabled person's independence," says center director Helena Mitchell. Founded two years ago on a $5 million, five-year federal grant from the National Institute on Disability and Rehabilitation Research, the Center is already testing its first prototypes. All of the devices are built from off-the-shelf components to keep costs down and accessibility high. Design priorities are informed by in-depth field studies and interviews. "Often, these kinds of devices are created in a vacuum by people who are pushing the envelope technologically," she says. "But it's important to always be thinking about the user." One system, called an "auditory display," combines GPS, a mobile PC, and headphones outfitted with a head-tracking sensor to help blind individuals navigate on their own. The GPS receiver pinpoints the wearer's location and the head-tracker monitors which direction he or she is facing. Meanwhile, the computer generates spatial sound signals, tones that the user perceives to be emanating from a specific direction. Once a path has been programmed into the system, the user then follows the sound cues like virtual trail markers to get to his or her desired destination. The Feature