Hi Antoine,
You can use the EyeX Controller with maintained accuracy when moving your head along all axes (x, y, z) as long as your eyes are visible to the eye tracker and within the so called track-box (the volume the eye tracker can track eyes within). This gives a freedom of movement of up to about 7-10 inches from the center of the track box, a point about an arm’s length from the center of the eye tracker front panel.