I'm looking into some mileage tracking apps so I can track my mileage at work. There are several on the market that work via gps. Basically you press a button when you start your trip and another button when you end it. My question is about how these apps actually track you. Do they track your location as the crow flies (i.e. they look at your start and end and calculate the distance straight between) or do they calculate based on the actual roads you have to take to get from A to B? I'm wondering if I'd be better off with just an app where I record my miles directly and don't mess with GPS. Can anyone recommend some good mileage tracking apps?