This version is based off the nRF52, which is still in preproduction as I understand it ( disclosure: I write firmware for the nRF51 for an IoT startup). Both

This version is based off the nRF52, which is still in preproduction as I understand it ( disclosure: I write firmware for the nRF51 for an IoT startup). Both the 51 and 52 can have a BLE DFU programmed into the chip, allowing over the air firmware updates, so you wouldn't need a JTag. Most companies lock this down with a secure boot loader, meaning you would need to be able to flash the device using a JTag (only $500!)