If you have an android phone this app's sound really useful. It warns when you get to close to the car in front, if you are drifting across lanes, and you can set up max. speed warnings. It's in beta stage, and is currently free to download. http://www.reghardware.com/2012/03/06/app_of_the_week_android_ionroad_augmented_driving/ Haven't tried it yet, but will on my way home from work today.