Up to 50 ft range to detect a person.
Device
http://www.amazon.com/Microwave-10-525GHz-Doppler-Detector-Arduino/dp/B00FFW4AZ4/ref=pd_sim_sbs_e_1?ie=UTF8&refRID=1882JQN656EEAW7G3GSM#productDetails
Needs amplifier circuit
http://www.limpkin.fr/public/HB100/HB100_Microwave_Sensor_Application_Note.pdf
Data sheet
http://www.limpkin.fr/public/HB100/HB100_Microwave_Sensor_Module_Datasheet.pdf
