The box can have any sensors connected but you must write scripts for reading them and publishing the results to a local MQTT queue. A Node.js application exposes these readings as a Bluetooth Smart / BLE service.
Scripts for reading BME280 and SDS011 sensors (temperature/humidity/barometric pressure and PM2.5/PM10 particulate counts, respectively) are provided in the mqtt-sensors folder.
Set up the OS and install the Node.js-BLE app as shown in the rpi-ble-services directory.
Connect the sensors and install the python scripts for reading them. Instructions in the mqtt-sensors directory (general README and bme280.md).
Some more information about wiring the sensors and the use of the companion Android application (direct link to installer HERE) can be found in https://github.com/VekotinVerstas/rpi-air-workshop.