Puck.js with Node-RED on Raspberry Pi

This comment http://forum.espruino.com/comments/13381021/ may answer some of your questions. If you point your browser to Node-RED on your RPi3, you can set up an MQTT input node that will read those topics and take whatever actions you want. For example, this is a NR flow you can import that simply reports MQTT messages to the debug tab.

[{"id":"76f88a3c.99fe04","type":"tab","label":"Flow 2"},{"id":"6892e216.8f6d2c","type":"debug","z":"76f88a3c.99fe04","name":"","active":true,"console":"false","complete":"payload","x":340,"y":60,"wires":[]},{"id":"503cfb7e.f411c4","type":"mqtt in","z":"76f88a3c.99fe04","name":"","topic":"#","qos":"2","broker":"98edcbd7.d02a98","x":110,"y":60,"wires":[["6892e216.8f6d2c"]]},{"id":"98edcbd7.d02a98","type":"mqtt-broker","z":"","broker":"localhost","port":"1883","clientid":"","usetls":false,"compatmode":true,"keepalive":"60","cleansession":true,"willTopic":"","willQos":"0","willPayload":"","birthTopic":"","birthQos":"0","birthPayload":""}]

A more sophisticated example might look for the temp topic advertising device temperature and update a gauge node that would be dsiplayed on the Node-RED UI