It's for HDD protection I guess. If it detects high speed movement (ie: gets out of the safe zone), the HDD stops and it prevents the HDD from the damage. Pretty nice. (Like if you drop your laptop...for example, you will be able to recover all the data most likely.)
However, as far as I know it only works with Windows, since it needs a userspace application also. On Linux, only ThinkPad supports it (thinkpad-acpi comes with recent kernels). Guess on Windows you would have a driver/app for this on your notebook.
Basically now the HDD protection is off, you can play with it.. like..
Of course there are no limits. You only have to learn how to code and write an app which uses this accelerometer out. Just think about what kind of apps/games are avaliable for the iPhone.