"RIM has done something very interesting with the touchscreen on their new BlackBerry Storm. As Phone Scoop describes it (and everything I write here is based on media reports -- I have no insider knowledge):
The big news about the display is the touch technology. First, it's capacitive, like the iPhone and the HTC G1. This alone is great news, but the real innovation is the true tactile feedback. The whole screen is essentially one giant physical button that you can press down for a gratifyingly real "click" action. There are no haptics or funny tricks here; just good ol' tactile feedback, and it works very well.
As you would expect, the click action lends a great deal to the experience of pressing virtual buttons and text entry. However, it also enables a whole new dimension (literally) in touch interaction. Capacitive touch technology requires no pressure; it responds to the very lightest touch. This means the Storm has two distinct ways to press the screen. A light touch is just a "touch", while a more forceful press results in a "click". This makes the Storm the first phone we know of with what could be considered a "3D" touch screen.
Link: Hands-On: BlackBerry Storm (see also RIM's official site and Gizmodo.)
The part above that I highlighted in italics is what I find most interesting. From an HCI-theory perspective, what RIM has done is transform the touchscreen from a two-state to a three-state input device, according to Bill Buxton's three-state model of interaction. (I am assuming that you can drag your finger while pressing on the Storm; if you can't do that then I'm wrong and it's not a three-state device.) That model is described in Buxton's 1990 paper from the Interact conference: A three-state model of graphical input (pdf). (He also describes it in chapter 4 of his more recent book-in-progress on input devices.)
The three states in Buxton's model can be described roughly as "out of range," "tracking," and "dragging," and he shows how this state transition model is very useful in understanding the differences between all sorts of input devices, including mice, joysticks, tablets, and touchscreens. The picture below (copied from his paper) shows the three states as they apply to a graphics tablet with a stylus, which is a three-state device." (Continued via Touch Usability) [Usability Resources]