The Phoenix Ambulatory Blood Pressure Monitor Project is a piezo film blood flow pulse sensor, very cool –
The purpose of the piezo film pulse sensor project is to identify and build a reliable, low power, low cost blood flow sensor. The sensor is intended for two proposed designs for the ambulatory blood pressure monitor (ABPM). They are: (a) an oscillometric cuff design (as a Korotkoff sound sensor) and (b) the blood flow velocity design.
Piezo Film Pulse Sensor – Link.