The following are possible process control and visualization software that might be adapted to work with the GCU. Advantages/disadvantages of each package or new software options should be added below.
Proview - http://www.proview.se/
Scicos - http://www.scicos.org/
OpenModelica [modeling language] - http://www.ida.liu.se/labs/pelab/modelica/OpenModelica.html
Ascend - http://ascend.cheme.cmu.edu/
LiveGraph - http://www.live-graph.org/
kst - http://kst.kde.org (Linux/Windows, please report back if you get this working, looks powerful)
RRDTool - http://oss.oetiker.ch/rrdtool/index.en.html (needs script to upate database, writes graph to file, for e.g. web serving)
Veusz - http://home.gna.org/veusz/
GNUplot - http://www.gnuplot.info/
- forum post on using GnuPlot for real time plotting: http://www.gekgasifier.com/forums/showthread.php?t=395
R - http://www.r-project.org (statistics package, graphing and data analysis)
Helpful R language reference: http://cran.r-project.org/doc/contrib/Short-refcard.pdf