A corner sensor assembly (10, 210) for attachment to a corner structure, said corner sensor assembly (10, 210) comprising: a housing (12, 212) having an integrated power supply (20, 220) positioned within said housing (12, 212); a first motion sensor (14, 214) operatively connected to said power supply (20, 220), said first motion sensor (14, 214) oriented to sense motion within a first field of monitoring, wherein said first motion sensor (14, 214) generates a first active output when motion is sensed within said first field of monitoring or a first inactive output when no motion is sensed within said first field of monitoring; a second motion sensor (14, 214) operatively connected to said power supply (20, 220), said second motion sensor (14, 214) oriented to sense motion within a second field of monitoring, wherein said second motion sensor (14, 214) generates a second active output when motion is sensed within said second field of monitoring or a second inactive output when no motion is sensed within said second field of monitoring, said first field of monitoring being different than said second field of monitoring; at least one visual indicator (18, 218) is operatively connected to said power supply (20, 220), said at least one visual indicator (18, 218) being changeable between an active state and an inactive state; and a controller (22, 222) operatively connected to said power supply (20, 220), said at least one visual indicator (18, 218), and said first and second motion sensors (14, 214), said controller (22, 222) receiving said outputs from said first and second motion sensors (14, 214) and changing said state of said at least one visual indicator (18, 218) in response to a change in said outputs from said first and second motion sensors (14, 214); wherein said at least one visual indicator (18, 218) is in an active state when said controller (22, 222) receives said active outputs from both of said first and second motion sensors (14, 214), and said at least one visual indicator (18, 218) is in an inactive state when said controller (22, 222) receives at least one inactive output from said first and second motion sensors (14, 214), wherein said at least one visual indicator (18, 218) is positioned within said housing (12, 212) and viewable from within each of said first and second fields of monitoring (11a, 11b), characterized in that the corner sensor assembly further comprises a plurality of magnet (24, 224) assemblies attached to said housing (12, 212) for attaching said housing (12, 212) to said corner structure. a housing (12, 212) having an integrated power supply (20, 220) positioned within said housing (12, 212); a first motion sensor (14, 214) operatively connected to said power supply (20, 220), said first motion sensor (14, 214) oriented to sense motion within a first field of monitoring, wherein said first motion sensor (14, 214) generates a first active output when motion is sensed within said first field of monitoring or a first inactive output when no motion is sensed within said first field of monitoring; a second motion sensor (14, 214) operatively connected to said power supply (20, 220), said second motion sensor (14, 214) oriented to sense motion within a second field of monitoring, wherein said second motion sensor (14, 214) generates a second active output when motion is sensed within said second field of monitoring or a second inactive output when no motion is sensed within said second field of monitoring, said first field of monitoring being different than said second field of monitoring; at least one visual indicator (18, 218) is operatively connected to said power supply (20, 220), said at least one visual indicator (18, 218) being changeable between an active state and an inactive state; and a controller (22, 222) operatively connected to said power supply (20, 220), said at least one visual indicator (18, 218), and said first and second motion sensors (14, 214), said controller (22, 222) receiving said outputs from said first and second motion sensors (14, 214) and changing said state of said at least one visual indicator (18, 218) in response to a change in said outputs from said first and second motion sensors (14, 214);