Navigon's MobileNavigator software app for the new Apple iPhone 3G S (Click to enlarge.)

After declaring last month that it would leave the U.S. market for GPS units, the company has now announced new software in the works for the soon-to-be-released iPhone 3G S. The downloadable app, called MobileNavigator, will be available later this month and will offer turn-by-turn directions—one of the feature upgrades on the new iPhone.

The Cars blog reports that two version of the software will be available: a Lite version with maps but limited functionality, and a full version with Navigon’s usual complement of features—reality view, turn-by-turn guidance, lane assistance, current speed, day/night mode, and points of interest. Prices will be available upon release.

Navigon is joining TomTom in jumping on the iPhone bandwagon. The latter recently announced plans to release its own app software for the next-generation phone, including a car dock, microphone, and speaker to fully mimic a standalone GPS unit. TomTom for the iPhone is set for a late-summer release.

Not planning to buy the iPhone 3G S? You can still get guidance from standalone units. We’ve just updated our Ratings of GPS navigators (available to subscribers), so take a look. —Nick K. Mandle