The Spacenavigator mouse is a staple anywhere professional CAD people are working, and it looks like it is a natural fit for a robot arm. According to [angrymop], the Raspberry Pi can read the ...
You probably want one in the shoulder of your robot arm, for instance ... The video is partly an ad for SolidWorks, and spends a lot of time on the mechanics of designing the parts for 3D printing ...