Yes, you can have a collision warning system for your car in the palm of your hand instead of an expensive option package. The iOnRoad application uses your smartphone's camera and some fancy algorithms to detect cars in front of you and beep if you get too close.
What you need to know: To use iOnRoad, mount your smartphone into a car dock without blocking the camera. I tested the app on city and highway roads using a Samsung Galaxy Note running Android 2.3 Gingerbread.
Once the app is running, a green line appears to indicate that iOnRoad is monitoring your headway distance. Close in quickly on the vehicle in front of you, and an icon appears over the car that shows the time gap, the distance from the car, or the car's speed. A green icon means you're a safe distance away; yellow signifies caution; and red means you're in danger. You can adjust the "threat level" of the alert in the app's settings.
The main app screen contains buttons that let you access the phone, navigation and music apps, a digital speedometer, weather and temperature, and a compass. The top of the screen shows a score of how safe you're driving. Other features include a car locator, a narrator who reads incoming text messages and phone notifications, lane departure detection and automatic driving detection, which lets your phone launch iOnRoad automatically whenever you start driving. You can run it in the background if you want to use other apps without losing iOnRoad's functionality.
What works: While driving in moderate city traffic and on shopping mall access roads, iOnRoad could detect the car in front of me and beep whenever I got too close. It might have beeped a little too often while on a congested highway, but never became annoying. There were no problems using iOnRoad at night.
What doesn't work: The app is actively monitoring headway space once the green lane-marking strip appears, and it can take awhile before you see it. When I tested iOnRoad at dusk on a rainy day, I drove miles before the strip appeared, and it showed up for only a few seconds.
The app touts lane departure detection on highways, but it never activated when I switched lanes or drifted close to the shoulder. There were some hiccups with iOnRoad's ability to detect the car directly in front of me. Occasionally it would track the car in the adjacent lane or it wouldn't detect the car until I passed it.
Bottom line: In city driving with normal traffic and no precipitation, iOnRoad is a nifty app to use.
-Dave Lee, Cars.com