Seat occupancy detector

A seat occupancy sensor comprises a pressure detection device (14) associated with a surface (10) of said seat (12) and a control unit (34) for communicating with the presure detection device. According to the invention said pressure detection device comprises a surface acoustic wave device (26) including at least one surface acoustic wave resonator (28) and an antenna (30) and said control unit (34) comprises an RF antenna (38) for remotely communicating with said surface acoustic wave device (26). In a first embodiment, the surface acoustic wave device (26) is adapted for detecting the pressure inside a sealed chamber (20). In a second embodiment, a pressure sensitive switching device (120) is connected to the surface acoustic wave device (26) so as to activate the surface acoustic wave device (26) when the pressure sensitive switching device (120) is triggered.