An energy efficient prototype for diagnostic grade mobile ECG monitoring is developed. The prototype is developed with commercial discrete components to demo a patient centric medical environment. The prototype uses a mobile phone as a gateway to transmit the measured ECG data back to the medical cloud: Bluetooth for ECG sensor to the mobile phone, while 3G/WiFi for the mobile phone to the medical cloud. Therefore, the patients are not tied to the hospital or home, and can go outside for common life. The prototype can calculate on the mobile phone the RR intervals. More accurate RR, QRS interval can be obtained from server. The platform can also analyze the non-linear analysis of heart rate variability in patients with congestive heart failure based on multi-scale entropy. The size of the developed ECG sensor node is 75 mm × 35 mm × 20 mm which is smaller than a credit card in area. The noise density of the amplifier is 22 nV/√Hz, and the total power of the sensor frontend is below 100 uA. For wireless transmission, the Bluetooth module with a micro controller consumes current less than 110 mA. The prototype can monitor ECG continuously for over 24 hours or with 3 weeks standby time.