A low cost solution for detecting the flow of water in a sink using a non-contact vibration sensor coupled with a computer vision system and a passive switched RFID tag that becomes active upon detection of water flow. In some embodiments, the water flow forms an active antennae system for the RFID tag. The sensor comprises a piezo electric film attached at the underside of a water receptacle, for example, a sink so as to collect the sound generated by water splashing or hitting the sink and a vision system using active detection techniques.