Rumor has it that a third-party GPS system for the iPhone will be coming before the year is out. And though the iPhone is already GPS equipped, it lacks turn by turn navigation, making this a likely developmental choice.
TomTom has already had some success running their navigation system on the iPhone noting, "it looks good and works very well" though they will have to "look more closely to Apple’s strategy before we can say more about what kind of opportunities this will bring us," according to a msnbc.com report.
At this moment, it's unclear as to whether or not the iPhone SDK will allow a GPS navigation app, but it doesn't seem that they are prohibited. Apple may very well develop their own GPS solution soon, but more likely than not, a third-party will beat them to it.
Holy crap, that’s cole and the freeway, that’s like 2 miles from my house…. this is a sign….