Detecting presence with infrared and sonar sensors
The Wireless Sensor Network Research Group has published a couple of articles regarding the detection of people using WSN. In the first one they use the infrared radiation which provides a PIR sensor to detect movement of objects which temperature is over an specific threshold. In the second one they have integrated an ultrasonic sensor which emits ultrasounds and receives their echoes, this method is able also to predict the exact distance to the object in the same way bats do.
