A surprisingly good ECG is possible using a single op-amp. The main idea is that you allow the simple circuit to amplify noise (mixed in with your ECG), send the noisy signal into a PC using the microphone jack of the sound card, then use Python to remove the noise in real time, revealing the ECG.

Project page: http://www.swharden.com/wp/2016-08-08-diy-ecg-with-1-op-amp/

YouTube demo: https://www.youtube.com/watch?v=AfirWls9Sys

Many people have found this python source code difficult to use due to its dependence on version-specific libraries. A simpler click-to-run EXE for Windows that does essentially the same thing (written in C#) is available on the Sound Card ECG project page.

Screenshot	Video Demonstration

This software needs certain libraries like PyQt4 and numpy, so the easiest way to make sure you have versions of everything that get along is to download a pre-packaged Python distribution. This software has been tested and works with WinPython 3.5.2.1 (not the Qt5 one)

• install WinPython-64bit-3.5.2.1 (not the Qt5 one)
• download this project and modify go.bat to reflect where your python.exe is
• build the circuit, plug it into your microphone hole, and run go.bat