An apparatus for detecting an object 20 in an area adjacent a doorway includes a plurality of transducers US1, US2 mounted proximate the doorway and a processor 40. At least one of the transducers US1 is positioned to repeatedly transmit signals T1 toward an area adjacent the doorway. At least two of the transducers US1, US2 are positioned to repeatedly receive R1, R2 return signals. The processor 40 is operably connected to the plurality of transducers for detecting, in the area adjacent the doorway, an object 20 by determining the object's: position based upon one or more determined distances d1, d2 derived from times between transmission of signals and reception of corresponding return signals; and/or movement based upon transmission of signals and Doppler shift in the reception of corresponding return signals.