STEVAL-WESU1 is a reference design developed and optimized to help designers implement the latest technologies in wearable and portable applications. The small form factor of the hardware allows it to be enclosed in a watch strap, so the user can experience a real activity monitoring system and immediately begin appreciating the sensor data acquisition, as well as all of the embedded hardware and firmware features, also thanks to the ST WeSU app available free of charge from Apple Store™ and Google Play™ stores. The Apps are based on BlueST SDK, available on GitHub. Advanced users can also further reduce the hardware form factor; please refer to STEVAL-WESU1 user manual for more details. The STEVAL-WESU1 firmware package is built on the STM32Cube software technology so it can easily be augmented with further algorithms. It runs on STM32L151VEY6 and includes the drivers to manage three sensors (LSM6DS3, LIS3MDL and LPS25HB), the Bluetooth low energy network processor (BlueNRG-MS) and the battery management ICs (STC3115 and STNS01). The firmware is freely available on www.st.com.