NAVIGON North America [$89.99 - iTunes link], just let us know that, fresh off adding text-to-speech for street names, they'll soon be adding real-time speed information from actual drivers on the road, traffic messages, road sensors and cameras, and historic traffic flow data to reroute iPhone users around problem areas.

Billed as NAVIGON Traffic Live, it will be available in October and sold as an in-app purchase to existing MobileNavigator users. The added functionality will run $24.99, but go for $19.99 special introductory pricing at launch. And as with the main app, there's no monthly subscription cost.

Will iPhone users be willing to pay more to get more? That remains a question. We've asked before for premium apps, and said we'd pay a premium price for them, and this is certainly an example of that kind of App Store model.

However, by aggressively adding new features so rapidly, NAVIGON is setting the pace when it comes to turn-by-turn GPS navigation on the iPhone. Users of up-front, subscription, and even crowd-sourced mapping apps will all benefit from that.