Google has posted a video (below) demonstrating Google Maps Navigation for Android GPS-enabled phones -- notice the lack of "iPhone" in that clause. With this feature, users can use their Android phone for turn-by-turn GPS navigation, including voice-based requests and the ability to receive voice directions.
Our friends at TechRestore noticed the video for us, and as they pointed out in a tweet, this could be why Apple recently purchases a map developer. In this video, Google Maps Navigation is being demonstrated for Android phones only, leaving Apple's iPhone out in the cold.
Third party GPS companies have addressed the GPS market for the iPhone, but Apple could be keen on not being beholden to Google for this or other map and navigation features as competition between the platforms heats up.
Google Map Navigation Demo Video