Yeah, though support is pretty limited though and worst of all, the axis are not standard and so there needs to be branches for basically every sensor/computer configuration to ensure Y+ is up and X+ is right. Coming from iOS land it's exciting until you realize it's going to be tricky to do widespread. Here's to hoping it improves soon though!
All Apple laptops since 2006 have had a sudden motion sensor to detect when the laptop is falling and lock the hard drive platters in place to prevent damage. Apple exposes this to software basically just because they can, AFAIK. And to support cool features like this.
It appears the new macbook air no longer includes the motion sensor since it was originally designed to protect the hard drive, and the new air is lacking one.
That's pretty awesome too, I could see this being great for mobile web apps, especially games.