In Connecting to Intel® Edison from Android* with Bluetooth* LE (BLE) describes a way to access BT via Arduino code but additional BT shield/kit is required.

The combination of a transparent OLED display, Arduino Nano Every microcontroller, HC-05 Bluetooth module, and a small LiPo battery results in a functional and versatile piece of wearable technology.

The HC-05, a Bluetooth to serial bridge, can be found for around $5 on the internet and therefore may be the cheapest way to add Bluetooth connectivity to your project. However, its default setting… ...