The app, for Nexus One and Droid phones running the Android 2.2 operating systems -- though there are plans to expand to other mobile devices -- starts automatically when you insert the phone into a car's charging cradle. Car Home is voice-activated -- though Roy Furchgott at The New York Times "Wheels" blog says the quality of the system is dicey -- and has six buttons on-screen that allow you to add location shortcuts or, conveniently, other car-related apps. According to Furchgott: "You can also add direct-dial numbers or directions to common destinations, like home and work."

The voice-activation and customization are the major selling points of the Car Home upgrade, the earlier iteration of which lacked these features.

Google's free apps are typically well-planned and well-executed, but their add-on value usually comes via Google's relentless focus on collaboration, and Car Home is no exception: Google has made it easy for software developers to link their own creations to work with the app.