Apple has been granted a patent (number 8274479) by the U.S. Patent & Trademark Office for a gimballed scroll wheel. An input device that includes both a movement detector, such as mechanical switch, and positional indicator, such as touch pad touch screen, and/or touch sensing housing is disclosed.
These two input devices can be used substantially simultaneously to provide a command to the device. In this manner, different commands can be associated with depressing a moveable member in different areas and a single moveable member can perform like several buttons.
Here's Apple's background and summary of the invention: "Several kinds of input devices are known for performing operations in a computing device. Some examples of input devices include buttons, switches, keyboards, mice, trackballs, touch pads, joy sticks, touch screens and the like. Each of these devices has advantages and disadvantages that may be taken into account when designing an input apparatus...| Read more »