Chromecast

Google Cast is a proprietary protocol released by Google in 2013.

Cromecast built-in or Chromecast for short, is the implementation of Google Cast in hardware.

Chromecast Audio allows for lossless transmission up to 24 bit / 96 kHz.

Google Cast enables you to extend your Android, iOS, or Chrome app to direct its streaming video and audio to a TV or sound system. Your app becomes the remote control to play, pause, seek, rewind, stop, and otherwise control the media.
Bron: https://developers.google.com/cast

Communication is over WiFi.
If your gear is not WiFi and/or Chromecast enabled, you can use a dongle.

You need a Google Cast-enabled app on Android, iOS, Chromebook or Windows to stream to a chromecast device.

In case of Windows, Google Chrome can do it.

If you want to send the output of any media player to a Chromecast try

Chromecast Desktop Audio Streamer

On Android you have a wide choice: Google Play Music, Spotify, Pandora, iHeartRadio, TuneIn Radio, Rdio, Deezer, Rhapsody, Napster, NPROne, BeyondPod, etc.

Any streaming audio services supporting Google Cast can send the audio to a Chromecast enabled audio system.

In this scenario your phone works like a control point.

It simply tells the renderer where to get the music from.

Your phone is not interrupted by the audio and the audio is not interrupted by the phone.

You can also cast the screen of your android phone to a TV.

References

Chromecast built-in - Google
Google Cast SDK - Google

Chromecast Audio $35

It was introduced in 2015.

Early 2019 Google decided to stop production.

Audio codecs

HE-AAC
LC-AAC
MP3
Vorbis
WAV (LPCM)
FLAC

Sample rate/bit depth: 24-bit/96KHZ

Network

Connectivity/Network: Wi-Fi 802.11ac (2.4GHz/5Ghz)
Wireless Security: WEP, WPA/WPA2

Outputs

analog (3.5 mm stereo)
Digital (Toslink)

Performance

What can you expect from a $35 DAC?
Certainly not stellar performance.

Archimago measured both the analog and the digital (Toslink) out.
He thinks the analog out is pretty fair.
The Toslink is rather jittery.

AmirM did the same.
The toslink is jittery but the results depends pretty much on the quality of the DAC.
In case of the Shiit Modi you see a lot of sidebands.
In case of the Topping D50, no traces of jitter at all.
Obvious the ChromeCast is high on jitter but a well designed DAC can cope with it.

Google Chromecast Audio - Part I: Analogue Output - Archimago's Musings

Google Chromecast Audio - Part II: Digital Output - Archimago's Musings

Review and Measurements of Chromecast Audio Analog Performance - AmirM

Review and Measurements of Chromecast Audio Digital Output - AmirM

Added 2015