ESRI is *the* player in GIS.
You can get a 42" touch overlay (for an LCD or Plamsa) for around $4K. We are putting one in our cIED training system. In our case we are using the touch screen as interface to the game engine.
Forget this though - just go straight to gestures without any screen. We have one of these systems set up at the Interactive Media division:
http://oblong.com/