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 produces. Therefore, a recent energy management chip of Linear Technology is used, the LTC3588-1. Using this chip together with a big storage unit constituted by a supercapacitor, lead to very positive results. The system could power the device for a few hours even without the presence of a vibration source. Energy harvest is an alternative to consider when feeding low power portable devices is desired.