What to expect?
As mentioned before, we actually host the application on your sandbox cluster too. You can take a look at https://quarkus-mqtt-integration-starter-drogue-quarkus-demos.apps.wonderful.iot-playground.org/
On this page, you should see a dashboard like shown in the following screenshot:
This dashboard shows the most recent received message from any device. If the message contained geolocation information, then it will also put a marker on the map. Only one marker will be shown at a time, so a new marker will replace any previous markers.
The data comes from a publicly available data stream, hosted on the Drogue IoT sandbox cluster.
You can subscribe to that data stream with a simple MQTT client yourself.