Wearable health and activity monitoring devices are used to enable prevention and early intervention in case of health problems. In order to be widely adopted, these devices must be comfortable, easy to use and provide meaningful, error-free data. This study presents a miniature real-time wireless monitoring system capable of acquiring tri-axis acceleration using an integrated accelerometer, one-leadelectrocardiogram (ECG) and temperature. Embedded data processing allows for on-device detection of heart rate and body position with a possibility of generating alarms and warnings based on thresholds. It is a wearable device, intended to be attached on a patient’s chest and to communicate acquired and processed data to a mobile phone used for visualization, control and further communication. We focus on extending the lifetime of the device through simplification of data processing algorithms and optimization of communication protocols. Presented experimental data verify the functionality of the proposed system by comparing with reference devices. Furthermore, we experimentally prove average power consumption of 1.86 mW during continuous ECG acquisition and periodic heart rate reporting and 16.6 mW for complete real-time burst data transmission at 0 dBm with missing packet retrieval.