From a practical POV I don't think you could ever, ever, ever get around the perceived privacy issue of using cell phones. (Maybe even a real concern.) As to t

From a practical POV I don't think you could ever, ever, ever get around the perceived privacy issue of using cell phones. (Maybe even a real concern.) As to the using the bus data I have run some tests using the SF Muni dataset (nextbus.com). The speed of the buses in the dense parts of the city doesn't correlate with the speed of traffic. They stop too often and the timing of the stops is inconsistent. Here in SF the buses often move over a fixed distance (20 blocks, Van Ness) in the same amount of time at 2AM and 5PM. Dash is a great idea (we own two!) but obviously the money hasn't worked out.