It is possible to graph inequalities on a number line or in the plane.
Shawn Godin supplied the first sketch (see isenegger.ca/GSP/greater_less.gsp) and I am not sure where I picked up the other (isenegger.ca/GSP/inequality3.gsp).
I have been collecting resources for Sketchpad - see mathfest.blogspot.com/2008/05/resources-for-geometers-sketchpad.html, including the mathforum discussion group where questions like this are routinely and professionally answered. If you need any help deconstructing the methods used in either sketch above, you can contact me through my blog.