likely two cameras, the first is the viewpoint that you see in the shot, the second is from the viewpoint of the sphere (like a camera on a tripod). you could do it with two takes from the two POVs, but 2 cameras would make it easier.
you could then use cc sphere on the shot from the sphere's pov to make the sphere. then some shading and a shadow to make it more real.
if you were going to experiment with this, you might try different wide angle lenses on the sphere camera, possibly as wide as a fisheye lens.