I can't find if such an app exists, but I'd buy it if it did... I'd like an app that can record my driving, much like a flight recorder. It could store just the last XX minutes of driving. I'm picturing the ability to record video and have configurable text overlays on the video showing GPS coordinates, street name, speed, heading, time, date, etc. It could even record and display acceleration in g's. On the iPhone 4, it would be cool if it could simultaneously record both the front and rear view using the dual cameras. Such an app would be very handy in proving fault in a traffic collision. It would be great for track days, too.