More than Arduino

Although it is true that the Arduino Primo is intended as an Arduino board that can be programed from the Arduino IDE, considering it as an nRF52 board with Wi-Fi and some other options might be interesting too. The nRF52 is a popular MCU for which many projects and applications can be found online. For instance, the open-source Apache Mynewt OS targeted at IoT applications and wearables runs on the Primo.

The nRF52’s radio is primarily targeted at BLE, but it can be used for custom protocols too. Nordic for instance provides an ANT+ stack. Note BTW that the chip is Bluetooth 5 ready.

 
The Arduino LED is on pin 9, not on pin 11
The Arduino LED is on pin 9, not on pin 11.

Conclusion

The Arduino Primo together with one or more Core satellite boards forms an interesting platform for IoT or connected applications. The tap-to-connect capability allows for easy deployment of the nodes while the Primo itself provides access to the internet. Software support for both boards and their processor is plentiful.
Of course, it is not necessary to use a Primo Core board with the Primo main board, both can very well do their own thing. Being low power and small and equipped with many sensors the Primo Core is perfect for unconnected (wearable) applications too.