The closest the 3G can come is using a compass app (third party, not apple's) that uses the accelerometer to determine the orientation of the phone. Basically you set the compass app to be calibrated to as close to north as possible, then you get a reasonably (relative to having no compass at all) accurate reading of the direction you are headed. It works in a pinch if you are able to properly calibrate it, but is no replacement for the real thing.