The CPRO button from Metawear deserves its name: only slightly larger than the button cell that powers it, it's a platform of Bluetooth Low Energy sensors, and it comes with an SDK that allows you to program it wirelessly with your smartphone. It's difficult to imagine anything simpler to develop a prototype for the Internet of Objects (IoT). This ultra-miniaturised circuit board connects to a smartphone and sends it some environmental measurements captured by its sensors: acceleration, force, angular velocity, magnetic field, pressure, altitude and temperature.

The software development kit (SDK) allows the use of the captured data, remote control, and complex filtering of or triggering on the captured data. The CPRO button is based on the nRF51822 SOC from Nordic built around an ARM Cortex™ M0 processor and a Bluetooth low Energy interface, with a 10-axis movement detector, all powered by a button cell. Apart from an LED and a push-button, the CPRO card has the following sensors:
• BMI160 accelerometer
• BMI160 gyroscope
• BMM150 magnetometer
• BMP280 pressure sensor
• LTR-329ALS ambient light sensor
• BMP280 temperature sensor.