You don't necessarily have to wave your arms around. I don't know how the g-speak works, but if it uses the orientation of the hand to do raycasting (as it shou

You don't necessarily have to wave your arms around. I don't know how the g-speak works, but if it uses the orientation of the hand to do raycasting (as it should), you can leave your hand comfortable by your side and not be bothered by having to raise your arms at shoulder level. The real pain comes when you try to apply 3D interfaces like g-speak to problems that are not inherently 3D. You get awkward interaction and a lot of wasted time. Real applications of 3DUIs include medical operation planning, virtual reality, scientific data visualization and architecture, just to name a few. Also, in most cases, gestural interfaces are not the most efficient way to do it.