There are no unsolicited event notifications, yet. I’d like to see them and have asked. In some other posts Samer has indicated they are considering them, if not already working them. I don’t have any info on what the mechanism would look like. I would think that the supplied apps would benefit from such a mechanism, too.
Until then I’m trying to balance overhead vs currency of display. I poll for general info every 15s (settable) and trigger additional requests whenever there is an action coming from my app so that displays updates quickly. Polling for specific info occurs more or less frequently depending on the type of info and the state of the controller.