You can simulate one of these yourself by getting a wide flexible plastic mirror (dimensions along the lines of 1:4) and bending it to be concave until you look

You can simulate one of these yourself by getting a wide flexible plastic mirror (dimensions along the lines of 1:4) and bending it to be concave until you look undistorted. Looking into this bent mirror, if you raise your right hand, the hand on your left side in the reflection will move.