Nokia N900 does not have rSAP Bluetooth profile which would allow connecting it to most of European carkits (VW, Skoda etc).
N900 runs linux based Maemo OS.
Project scope is to develop installable library/software that would make it possible to connect Maemo based device to car kits using rSAP profile.

Just a note that logics from Symbian source could be used.
Link to problem: http://maemo.org/community/brainstorm/view/rsap-remote_sim-support_for_n900

p.s. Phonebook synchronisation to car phonebook development is also possible on additional agreement.