Piezo Film Pulse Sensor

I just realized that none of the pulse watch that we had discussed weeks ago measures the pulse from wrist. Both from Polar and Sigma Sport always use the chest strap to take the EKG signal and send it to the watch. And this is not what we want.
Our ideal pulse watch should look like a normal watch, that sense the pulse from the inner part of wrist. Unfortunately, this kind of watch is only available as blood pressure unit.

I found an interesting experiment from internet, the project name is Piezo Film Pulse Sensor. A simple piezo film detects pulse-caused skin movement, and the output signal (EKG like) can be used directly to count pulses over a period of time. The project description is here.

The next day, one of my supervisor bought a pulse watch from Tchibo. He was thinking about not using the strap on chest but at wrist. I tried to place it here and there, but the strap didn't recognize any signal if you put it at wrist.

Then came an idea to use the strap after all, but not the watch. Based on experience of another AmI project, they simply took the radio freq. receiver circuit from the watch, the circuit provides the pulse signal as output.

So, now I can forget about making my own Pulse Sensor and use the Tchibo pulse watch instead.