Build Your Own ECG-EKG Unit | Nuts & Volts Magazine
The Do-It-Yourself Electrocardiogram | SpringerLink
Electrocardiography for Cheap: DIY ECG Uses One LM741 Op-Amp, Five Resistors, and 'Penny Electrodes' « Adafruit Industries – Makers, hackers, artists, designers and engineers!
How to Build an Electrocardiogram Machine (EKG) | PCB | Maker Pro