A quick heads up, folks, that you should now (or very, very shortly) have the latest version of Google Play Services on your phone. This is the thing that lets other things do things on your phone — and all without needing a full-on system update, so it's kind of important.
And as was mentioned earlier this month, this update opens up the Google Cast SDK, which allows apps to easily stream from your device to the TV. There's also an improved Google Drive API, and more.
You don't have to do anything to get this latest version — just sit back and it'll come to you automatically if it hasn't already. And for those whose patience may have been lacking, the earlier version that pushed out should be overwritten by this one, so all's good.
Source: +Google Developers