Espruino and IfThisThenThat...

For receiving webhooks without messing with firewalls etc use a public webserver to receive the request then poll that server for the data? My example is PHP - maybe be better in Go or Node.js, depending on how realtime you needed the thing to feel?

<?php 
const PRIVATE_KEY = "my_private_key";
// Authenticate
if(!@$_REQUEST["key"] || $_REQUEST["key"] !== PRIVATE_KEY) {
	header('HTTP/1.0 401 Unauthorized');
	echo 'HTTP/1.0 401 Unauthorized';
	die();
}	
// Handle request
if($_POST) {
	// Update data and write to a file - validation maybe - but it should be data you expect
	file_put_contents('data.espruino', json_encode($_POST));	
} else {	
	// Get data from file, set headers and display
	header('Content-Type: application/json');
	echo file_get_contents('data.espruino');
}