Last week Michael and I went to the Hannover Fair, and we came round the 3DConnexion stand. I use a Spacepilot when doing Solidworks modelling, but since Michael didn't know these devises we had a good and proper look. What we saw was a "rugged" mouse that was in the user console of a small KUKA robot.
Further talking led to Michael giving in and buying a mouse which in turn resulted in the use of a 3DConnexion mouse as input for Machinekit.
see this thread on the Machinekit google group
Here is a video with stickers on motors driven by the Mouse: