This. My recent encounter in this space was a Nordic NRF51822 BLE chip bought as a 3$ breakout board from Aliexpress, wiring it via STM32 and compiling it using

This. My recent encounter in this space was a Nordic NRF51822 BLE chip bought as a 3$ breakout board from Aliexpress, wiring it via STM32 and compiling it using GCC and MBED ...and skipping over the expensive official compiler. The future is mobile!