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So you might be thinking that measuring tiny changes in acceleration could not be really useful. However this is not the case. This information has many uses.

We all know gravity is constantly pulling all objects to the ground. Even when a object is at rest it has a measurable amount of force pulling it toward the ground.

The iPhone and iPod touch have accelerometers on 3 primary axes. An accelerometer measures changes in velocity along a single linear axis. An accelerometer simply measures changes in velocity along a single linear axis to provide data on its position in 3D space.

Then by tracking which accelerometers are registering this acceleration, and the extent of that acceleration, you can then apply this orientation as input to your application.

The most basic use of this information is to monitor the current orientation and to notify your application when that orientation changes. If your application’s interface can be displayed in both landscape and portrait mode, you should incorporate view controllers into your basic programming.

You can also the data to detect the device’s orientation or to detect other types of instantaneous motion, such as the user shaking the device back and forth. You can then use this information as input to a game or other application.

This is part of the technology at use in the Nintendo Wii. The popular gaming console from Nintendo. I think it also has many applications outside the gaming industry. Those are discussions for another time and another forum.
 

I have to admit, I always used to laugh at people playing video games back in the day who would tilt themselves and their controller in hopes of being able to steer just a little bit further. Now this is not only possible, but it's part of some games. This new control function allows a whole new set of control possibilities.

The accelerometer can not only be used for changing the views of a 2D picture, but also for viewing something in 3 dimensions. The iPhone has good 3D graphics and an inventive new way to view them. By allowing the user to tilt the phone in 3 dimensions, you can view an object from all angles. I saw a video of what someone did with a Nintendo Wii controller to create a full 3D experience by tilting and changing the viewpoint. I'm sure with the right programming, you could achieve the same effects on your iPhone. You can view the video on Youtube HERE. It's worth taking a look at and may give you some inspiration.