Bloomberg reported that Apple was working on some new kind of sensors that can detect different levels of pressure. Now a patent for that has surface.

The patent, unearthed by Apple Insider, uses a piece of hardware that can trigger different UI functions. It depends on how hard the user presses the glass of the screen.

The "Touch-sensitive button with two levels" appears to suggest that it's actually about physical buttons, but what Apple is really talking about is that the technology can be applied to a touchscreen coupled to an actuator.

The image above shows how it works in action - as the button's depressed, two or more thresholds can be reached, and the device is doing something different depending on which threshold is broken.

What could it possibly be used for?Apple Insider suggests one particularly cool idea:
[W]ith support for more than two threshold levels, the patent would be able to control a host of device functions. It can be imagined that a user would be able to turn on a device, locate and open a mail app, navigate to a message, reply and back out to the home screen, all controlled by minute changes in pressure. This "drilling down" into an app is not mentioned in the patent language, but is illustrative of the possibilities afforded by the invention.
It's worth noting that while there's a patent, that doesn't mean you'll be seeing this in an iPhone anytime soon. [USPTO via Apple Insider]