From Battle Bricks: This is a demonstration of iPhone to Lego NXT Robot communication via the Safari browser and Lego’s Light Sensor. To build this, you’ll need a laptop, two iPhones, and a Lego NXT Robotics Kit. First, build your robot. Second write some Java LeJOS Robot code. Third write some Google Web Toolkit web application code. Fourth, plug in your iPhone into the robot, and use either a browser or another iPhone to drive the Lego Robot.
While the demo is a hack and may leave something to be desired, the increased I/O API options on the iPhone 3.0 will allow more functionality for these types of applications.