Yes but it's not something the N900 can do innately that any other product couldn't, neither can your car in its default ability probably).

For example, people have done hacks where they attach a cheap mobile phone to their car's ignition so they can call the number to start it (or send a text, etc..). Likewise it's probably possible via bluetooth. But it's not something that can be easily done without some knowledge of how a car works.