Not sure about iPhone, but on Android, all contacts (among other information) can be sync'd with Google automatically, so in the event you switch phones, all you have to do is add the Google account to your new phone and *presto* you are done. No going between phone, laptop, PC, Mac, iTunes or whatever, all that is done on the phone itself; no need for any external devices to accomplish such a simple task. Further, if you want just specific contacts in-car, all you have to do is link those contacts to your phone, select which contacts to display, and those can be sync'd with the car. Again, all on the phone; no external devices required to accomplish.
Syncing contacts to your car is a separate issue; all that needs to happen is transfer of your phonebook (whichever one you select) to the car via BT. Granted, if you change, edit or update your contacts, you need to re-sync with the car so it can reflect those changes if so desired.
