I was looking around the site and couldn’t find any information about the Apple laptops’ built in motion sensor, so I am writing what I have found. As far as integrating this motion sensor into to Cocoa apps, there are two implementations I could find.
This is some form of library for interfacing with the motion sensor. However, it is not Cocoa specific and does not support all laptops with the motion sensor.
This is a C framework for using the motion sensor. It supports all current platforms (I’m assuming that it does not yet support the General/MacBook Air, however.) It is the code written for the software General/SeisMac. If you have experience with Cocoa, or even C, it should be very easy to implement. If you are having trouble, sample code is included.