Triggering an action on a Pi when the button is pressed

@joakim thanks for that. A couple questions...

where is the Bluetooth object documented? It looks like a Serial object, but I don't see it mentioned on the reference page - https://www.espruino.com/Reference

I've got the node.js code working to the extent it connects to my puck, gets the appropriate characteristic and waits for data to be sent over. However nothing ever arrives from the puck. I've confirmed the puck side is working as, in the web ide, when I press the button, the Bluetooth.write() does result in something appearing in the web console.