Based on Onitsch Cartoons, he can measure hetbeat using piezzoelectric by taped the sensor into his finger.
Its using arduino board and make it works great without noise. Here is the skecth:
Connect piezzoelectric into A2, or may another Analog input pin by change A2 code above into another Analog input. For fine result, it can be filterred and gained using following schematic. The schematic is from amgalbu whose post his article into element14 community. He is using oprocoupler instead of using piezzoelectirc
The basic idea is that the operational amplifier sums up Vcc/2 with the amplified DC component of the Vsensor. Vcc/2 is obtained through the R4/R5 partitor. The AC component is measured on the C5 capacitor. This signal is amplified by a factor of 330 (R1/R2). The RF1 trimmer will make it possible to fine-tune the gain (amgalbu)
I have not test it yet, but I’m sure it will be working great. I just need a time to check it out