pedestrian detector for traffic light pedestrian waiting area

i am looking for device using rasbury Pi with camera to mount on top of traffic light pole 3m high facing down to detect pedestrian waiting to cross the detection area is 4m x 8m and this area can be set up by phone pictorially as detection zones. should reject shadows and other false detections and work night and day. rasbury Pi has a package including camera which does have good night vision and cheap so best to use this.