If you searching a tool for Windows, Linux, OSX and your windows mobile device…you may want to take a look at this:

*“SpaceTime 3.0 by SpaceTime Mathematics is a revolution in mathematics software with 2D, 3D, and time graphing with MobileCAS® for algebra and calculus. With features only available in Mathematica and MATLAB, SpaceTime is the most powerful cross-platform mathematics software ever developed for computers and mobile devices.*“

Source: http://www.spacetime.us/

also available for PalmOS…