If you’re having trouble getting around town and need turn by turn guidance, you can finally turn to TomTom, one of the biggest names in the industry, on your iPhone. The navigation company has finally released the app they debuted with the iPhone 3GS.

The app is one of the more expensive in the App Store, and certainly at the high end of the navigation price range, at $100. That does not include the car kit, which adds a speaker, an audio output jack to integrate with your car stereo, and a microphone for using the phone while your TomTom is active.

I think the real dealbreaker with this app is going to be how it handles phone features. Unfortunately, the iPhone doesn’t allow multitasking, so your TomTom will close when you receive a phone call. That could suck really, really hard if it can’t reposition via GPS quickly enough. On the other hand, if it works well, it could be a pretty sweet deal for those of you in the market for some GPS help.

Being that TomTom showed off their turn by turn navigation system at WWDC, and being that AT&T has hardly mentioned their Navigator app in recent memory, it seems odd that AT&T would be the first to release a turn by turn navigation app.

They were, though, in a free app download today. Don’t let free fool you. The app will add a $10 charge to your AT&T bill.

The application was developed specifically for the iPhone 3GS but it will work with OS 3.0 on other iPhones. The app gives you turn-by-turn navigation, updates traffic information and will let you search by your location for the cheapest gas.

AT&T may have made a smart play here, giving them the early adopters. I’ll be interested to see whether other turn-by-turns run for a similar monthly fee.