Which apple mobile devices have a magnetometer? I thought that the iPod touch had one but I think I am mistaken.
Do all devices with GPS have a magnetometer? Do all devices with a magnetometer have a GPS?
The iPhone 3GS and iPhone 4.
An easy way to check is with this class method. I wrote a little app and ran it on a few devices I had lying around, and it looks like only iPhone 3GS+ (so iPhone 4 as well) have one right now, although I've seen sketchy evidence that pieces of the Compass app exist in touches.
来源：https://stackoverflow.com/questions/4227272/apple-devices-with-magnetometer