The latest update to Google+ caught a few people by surprise today when it enabled a small Chromecast button in the interface, letting you toss your Google+ stream up to your TV. Though the Google Play changelog doesn't indicate the change, we're seeing a Chromecast button on our own devices and many other people are too.
The functionality is pretty simple, though — you can connect to a Chromecast and have it automatically loop through recent Google+ posts from your circles, only giving you the option to pause the auto looping or seek through posts one at a time. We'd expect this to expand over time.
It's likely more useful as a casual screensaver to have on your TV than an active way to view content — the phone or tablet itself will still be better for that — but we'll never turn down more Chromecast functionality in our apps. The latest Google+ update is rolling out in the Play Store right now, so be sure to check if you have the latest update from the link at the top of this post.