To avoid invasion of privacy issues, the only time it will be used, Huber says, is after an owner notifies police that his vehicle was stolen.

"When police have the vehicle in sight and feel they have safe access to getting it, they will then notify us at OnStar,” Huber said. “We'll take the power out of the car and turn on its flashers to alert others nearby to beware of a stolen car."

Cars scheduled to get the new system include the Chevy Silverado, Tahoe, Suburban, Equinox, Avalanche and Impala, Cadillac SRX, DTS, CTS, Escalade, Escalade EXT and Escalade ESV, Buick Lucerne, Pontiac Torrent, Hummer H2 and H2 SUT, Saturn Vue, and GMC Sierra, Yukon and Yukon XL. The service is free during the first year of ownership, but after that it’s part of a $190 package.