As you may know, Thursday is patent application publication day (try saying that 10 times fast), and yesterday's crop of documents included several Apple patent filings. AppleInsider took a gander and has details on one of the applications. This particular one discusses an electronic device that could enter "security mode" or transmit a security signal based on vibration or acceleration readings, among other things.

We've seen a number of mentions of mobile device security and safety from Apple lately, including device locators and biometric sensors, so the company seems to be on a bit of a kick. The most recent patent filing discusses a system that would put an iPod or iPhone into "lock-down mode" if certain vibration or acceleration levels were detected, and might also call or e-mail an external security service (or perhaps any external source) depending on the level of vibration or acceleration involved. Owners of the device would also be able to enter a code to bring the device out of the security mode.

At first, the system sounds a little silly—it's unlikely that an iPhone thief would vigorously shake the device just for fun—but there are some situations in which it might make sense. For one thing, having your iPhone call the police if huge acceleration levels are detected might help if you're in a car accident. You could also set your iPhone to lock whenever someone picks it up, in case you need to leave it in a gym locker or something. Still, the number of uses for something like this seem a bit limited, so it's unlikely that this will appear as part of the next iPhone revision.