I use the service at Pusher.com, I created some basic AGI’s that send the message to a listener on the web side. Pusher.com has examples.
Been running this way with 1000+ calls a day for a few years with ZERO failures that I can blame on Pusher. Far more reliable than I thought when I first considered this product. Saved my bacon back then from having to write something by hand back then with little knowledge of HTML5 web sockets.
I am about to re-write my own stuff though and will likely use socket.io with another add-on library I found but I forgot the name at the moment. Anyhow, socket.io would be my recommendation, you can notify the listener from an AGI script, at least that’s how I am planning on doing it.