Open hardware graphing calculator
There are plenty professional graphing calculators around that may satisfy your needs. But if you want more then there is no problem at all. Check out this graphical calculator with large touchscreen.
Calculator is powered by Beagle Board which is based on Arm Cortex A8 microcontroller. Calculator runs a linux where R software takes care of statistical computing. It also handles graphs and plots with lots of parameters. Sounds like real fun.

