The project aims the implementation of an electronic system integrated in a wrist strap capable of interact with several communication technologies such as: Bluetooth and Near Field Communication (NFC). In the present project a power system is studied as well as the NFC communication protocol. To power the device a recent energy technology is approached: Energy harvesting. More specifically, a piezoelectric generator is used to convert the vibration energy into electric. However, the piezoelectric cannot power the device only by its own because it needs a system to manage the energy that...