Is Junxiao in the Room? Presence Detection with nRF52 Bluefruit

I recently obtained some Adafruit Feather nRF52 Bluefruit LE boards. The main chip on this board is the nRF52832 from Nordic, which offers Bluetooth Low Energy (BLE) communication, but does not have WiFi. Adafruit made a nice Arduino core for nRF52, so that it can be programmed easily with the familiar Arduino environment.

Incidentally, this isn't the first BLE device I have. Many small battery-powered devices, including the Fitbit Alta HR tracker I wear daily, uses BLE for communication. This means, I could use the nRF52 board to answer one question: is Junxiao in the room?