From: takveen on
Many times people bump into each other from the person coming from the
other side of the wall. With this device place at the corner, person
coming from the other-side of the wall will result in flashing red
light on the opposite side as shown in the figure above. Very
innovative approach towards solving a common day to day problem.

http://www.progneer.com/wp/information_more_public.aspx?search_fd0=72157