Unfortunately Google Maps won't be part of the package due to licensing issues, but developers will be free to use maps sourced elsewhere. That's likely to raise the price of any navigation apps for the iPhone, as maps aren't cheap to develop or license. But it's a start.
What does this mean for the average iPhone user, or motorist, for that matter? It means that a new level of convergence is upon us. We've already integrated our phones with our cars via Bluetooth, but now the technology is flowing back the other direction, with GPS navigation coming to our phones.
Practically, it also means that you can find your way around familiar or strange landscapes with the aid of nothing more than your phone, eliminating the need for another standalone device that you're tempted to leave in your car - and that tempts thieves to break in and steal it.
It also prompts us to start wondering about what the next step will be - how tightly integrated can cars and phones get? And even if they can get more closely bound up, would you want them to? Sometimes it's nice to just turn a key and drive.