Automation ideas

Cast-web basically sets up your Google Cast devices as selectable speakers for any audio output in SmartThins.

Every other SmartThings Smartapp that works with SmartThings speakers can now use your Google Cast devices. Apps include many community Smartapps like BigTalker2 and even official SmartThings apps like SpeakerNotifyWithSound (defunct) and Speaker companion.

All of these features are available to Google Cast devices with a screen (Chromecasts, etc.) and without one (Google Homes, Chromecast audios, etc.) and even groups you created in the Google Home app. 

Stop my Chromecast audios when I turn on the TV

 

More ideas coming soon.