A quote Jacob Appelbaum "Smartphones are tracking devices that make phone calls." shows that the moment you start to use a smartphone, tracking movement about you becomes available.
This data is requested and used in many applications on your phone, and not only in the most obvious ones that guide you to your destination.
The speed of your movement can be used to identify if you are walking, cycling or driving. If you compare the paths with roads and railroads, you can know if you were on a bus, train or metro.
It's quite easy to see the differences between your mobility during workdays and holidays.
This wealth of mobility data over time is so powerful that it can indicate if you have kids, an affair er which religion or sexual preference you probably have.
Using this data can help you reduce the amount of time you spend in traffic, give suggestions to shift from car to bike or public transport when suitable, suggest nice walking routes in your neighbourhood or during your citytrip, or find the safest cycling route given the current traffic.
Having all this information on your data-pod enables all these and many more applications to serve you better and in new ways than is currently already possible