Google Chromecast Audio: Stream your favorite music with Google Chromecast Audio. Simply plug into your speaker's auxiliary input and connect to your Wi-Fi network. Then just tap the Cast button from your favorite apps on your phone, tablet or computer to cast songs, radio stations and podcasts to your speaker.
Audio version! This little guy works very well with so many apps out there. Just plug in the 3.5mm into any audio source (speaker system). Then use various apps to connect.
Only thing that's no good is how Spotify on a computer (desktop or laptop) requires you to connect to the Chromecast on your phone's Spotify app first, only then does Spotify work with it on the computer. It is important to note that this is entirely Spotify's fault, though, since it is their software. So 5 stars all the way for the Chromecast Audio and its capabilities!
Note, the regular (video, not audio) version is completely different in terms of what and how it connects to various electronics. This audio version is for audio only (duh). No HDMI or anything, just a 3.5mm wire.