Electrocardiography (ECG) is a test that measures the electrical activity of the heart. The use of ECG for recording in ambulatory settings is becoming more prominent due to an increase in in-home monitoring. By virtue of the ambulatory nature of the recordings, artifacts have a large effect on the signals, with the most significant artifact a result of motion. This paper describes an accelerometer system used to detect differential movement between the recording electrodes on the body. This system is then used to determine a Quality of Signal (QOS) metric for the ECG signal. The results show that the use of differential movement of the recording electrodes with respect to one another is a better representative of the motion artifact, then overall body movement. This simple Signal Quality metric is used to more accurately flag the appropriate noisy ECG data which can be rejected from the signal. The simplicity of this system also allows it to be easily embedded into any in-home monitoring system.