If you've done any traveling, or just needed directions to a nearby restaurant, I'm guessing your iPhone has already saved the day a few times over with it's built-in GPS navigation system.
You can hone in on your current location by tapping the GPS locator button on the lower left of your Google Maps screen.
And you can search for nearby locations, and the iPhone will give you step by step instructions for getting there from your current location.
I've used the iPhone's GPS in several major cities across the US, in Zurich, Switzerland, and in a couple weeks I'll have the chance to try it out in Frankfurt, Germany on my next business trip. It's kept me from getting completely lost on more than a dozen occasions.
That's all fine and dandy, but just how accurate is the GPS for tracking your current location?
I did a little test today by walking around the block at my office in downtown Portland. The trip around the block is exactly 0.2 miles, and I took screenshots of the iPhone every few seconds while the GPS tracked my position.
Then I put the screenshots together into a video using Camtasia (which I highly recommend), and uploaded the video to YouTube.
As you can see in the video, the GPS tracking system did a pretty good job of tracking my movements around the block.