This chapter aims to present step-by-step guidelines and practical considerations in designing, constructing and testing a complete, simple, user-friendly, energy-efficient electrocardiogram (ECG) data logging system that is low cost, aimed at hospitals in developing countries. It provides a way to extend mobile phones’ processing and interface capabilities with external sensors to create a low-cost ECG device. To capture and display the digitized ECG signals sent out from the USB microcontroller interface on a Physical daily activity or phone, it is first necessary to determine how a software application can capture such signals. Work done by the UN Foundation shows that governments, companies and nonprofit groups are already developing mHealth applications to improve healthcare. The decision to use a USB interface came about due to its widespread and almost universal popularity and usage in mobile phones and personal digital assistants.