(via http://www.androidpolice.com/2011/10/15/ionroad-takes-most-of-the-thinking-out-of-safe-driving-offers-augmented-reality-using-your-androids-camera/)Bringing to the Android Market what I consider one of the only useful augmented reality apps in existence, iOnRoad has introduced iOnRoad Augmented Driving. This app utilizes your Android device's rear camera to have a look at traffic in front of you, and, using complex visual algorithms, it determines headway, speed, direction, and potential traffic threats.
What's more, the app still keeps watching, and keeps you abreast of any potential dangers while running in the background, meaning you can switch to your music player, messaging app, or phone, and still get alerts from iOnRoad.