Whether people want to get a standardized body shape or to live a healthy life, fitness is the new trend and, hence, physical activity monitoring. Indeed, it is clear that people should avoid sedentary behavior to prevent several chronic diseases such as type-2-diabetes, cardiovascular diseases and even cancer. Furthermore, some disease push sick people to maintain a certain amount of physical activity, on body parts where muscle atrophy occurs. Nowadays, people live longer, but not in good health during this extra lifetime and the "silver economy" driven by seniors is trending. To meet this demand, we have designed a wristband with a fully-featured RadioFrequency IDentification (RFID) Near-Field Communication (NFC) controller. This device with associated algorithm is equipped to measure a signal that could be named as "movement quantity". Calibration between this signal and the Metabolic-Equivalent-of-Task (MET) from a professional indirect-calorimeter is seen to be in agreement, proving the feasibility of a simple, low-cost and low-energy MET sensing device.