For both Audi and BMW, that means T-Mobile, so if the car happens to be in any of the many areas where the nation's fourth-largest carrier doesn't provide service, the feature will not work.

Voice-recognition technologies have improved enough to become an economical addition to the automobile, on a wide scale. Such systems are intended to allow the driver to interact with the car with minimal distraction and to perform many basic commands.

One of the first companies to commit to voice recognition was Ford, which created the through a partnership with Microsoft. The technology is available on a wide range of vehicles at prices that put it within the reach of many consumers.

Other companies, such as Audi, BMW, and Mercedes, all offer similar systems, though mainly in higher-end models.