Orbit Optical Trackball
If you’re looking for a simple way to transition from a mouse to a trackball, look no further than the Orbit Optical Trackball designed for both Windows and Mac. It offers better ergonomics, with less wrist and hand movement that will ease the pain of repetitive-stress injuries. Optical tracking technology delivers precise cursor control at the touch of a finger while the ambidextrous, two-button design provides a familiar user experience for mouse converts. TrackballWorks software, a free download on Kensington.com, offers you the ability to assign specific button functions and create a customized productivity experience.
More information: http://www.kensington.com/us/us/4493/k64327f/orbit-optical-trackball#.VwVe23pzItA