Having been in developer preview since last year's Google I/O, an SDK to enable devs to stream content from mobile and web apps to TVs using the Chromecast digital media player is being rolled out for iOS, Android and Chrome developers.

Google Cast enables multi-screen experiences and lets a user send and control content like video from a small computing device like a phone, tablet, or laptop to a large display device like a television.

This technology relies on the Chromecast dongle, that has been on sale in the US for the introductory price of $35 since July 24, 2013, plug into your TVs HDMI port. 

The sender may be a phone or tablet running on Android or iOS, or it may be a laptop computer running Chrome OS, Mac OS, or Windows. A sender application running on the sender device uses the Google Cast API appropriate to its operating system to discover and transmit to the receiver application running on the receiver device. You can use the sender APIs to enable your Android, iOS, or Chrome app to send content to a large display.

The receiver device is optimized for video playback with a receiver application that receives data over Internet Protocol and transmits it to the television. The receiver API lets you customize the messaging between the sender and receiver applications for authentication and other scenarios.

The release of the Google Cast SDK is intended to make it easy for devs to bring their existing content to the TV as well as opening up new opportunities for apps that can benefit from a large, high definition, display.

In this video Paul Carff, a developer advocate in the Chromecast team, provides a brief overview and shows how get started.

For simple media applications, the SDK provides a default media player that can play back HTML5 media content, which can be customized using CSS. 

For non-media applications, or for more flexibility and design options, you can build your own custom receiver application using standard web technologies. With a custom receiver you can build virtually any application while including support for many streaming protocols, including MPEG-DASH, HLS, and Microsoft Smooth Streaming, all of which are available in the Media Player Library.

The GitHub Google Cast repository has sample apps for Android, iOS and Chrome. For Android, a Cast Companion library is provided on Google Developers to make integration of Google Cast even easier.

The Google Cast SDK for iOS is already available while the Android SDK will be available shortly as part of the Google Play services 4.2 update , which will shortly. For Chrome it will be available through the Google Cast browser extension which has started to roll out.