Awhile back we showed a demo video using an iPod Touch to drive around of a PR2. It was a fun experiment, but it relies on a proof-of-concept that's not quite ready for primetime.
Srećko Jurić-Kavelj of the University of Zagreb showed us that there's more than one way to get data from an iPod Touch into ROS. Instead of cross-compiling ROS onto the iPhone, which is still very difficult, he used the open-source accelerometer-simulator project on Google Code to receive the accelerometer on another computer. He was then able to easily adapt a sample Python script to broadcast that data as a rospy node.
You can see the results here as he drives around a Pioneer 3DX: