Nokia appears to be looking into 3D multitouch systems, if a patent filing is representative of its current research interests. The Finnish phone giant has applied for a patent for a 3D multitouch interface that would record pressure as well as two dimensions of location info.
The system is built with a combination of a capacitive touchscreen and a few force sensors that measure the strength of your pushes. The direction of that force is also able to be recorded, so strokes can be accurately represented on such a screen.
It's not clear when the technology might make its way into commercially available gadgets - it's likely to be some time. However, when combined with some of the haptic touchscreen prototypes that the company also has in its labs, we could end up with a phone screen that you can push, but can push you back!