I'm curious; how did you know that?

Edit: Ah, of course it's in the source.

This is not true. MacBooks all have a Sudden Motion Sensor which has an API that will give you live accelerometer data. Here's a quick list of apps/games that use it:

http://modmyi.com/forums/mac-gaming/800715-sudden-motion-sen...

And here's an open-source Obj-C library to get the data:

http://www.suitable.com/tools/smslib.html

To access the data via JavaScript you can just listen for the "deviceorientation" event.

http://stackoverflow.com/questions/4378435/how-to-access-acc...

Actually, a lot of laptops including Macs do have an accelerometer. They use it to detect possible impacts and park the hard drive heads. Probably will be going away with SSDs.

http://support.apple.com/kb/HT1935

I know it's not quite the same, but MacBooks do have sudden motion sensors.

See the "smackbook": https://www.youtube.com/watch?v=6uvQTTPr9Rw

As far I know MacBooks without SSD have a chip that can detect movement. Once the chip detects movement that is too fast it will turn off the hard disk to avoid damage. This chip can also be used with a C API.

MacBooks have had accelerometers since the titanium Powerbooks.

They were used to park the hard drive heads in the case of sudden movement.