Pretty much anything with a screen in it in my house has a ChromeCast attached to it. We use them endlessly for Netflix, Youtube, and Plex. I also cast audio from my phone to speakers with ChromeCast Audio. It would be an interesting option for any Mycroft skills with audio output, such as NPR News. Additionally, since you’re getting more and more into displays with the Mark II, you could use a ChromeCast for video output for any skills. For example, you could put the weather forecast up on the screen whenever someone asks what the weather is like. ChromeCast is a quick (not sure how easy) way to add video output to pretty much anything.
I did some testing with chromecast some time ago, and chromecast is rather picky in which video it will play. Most mp4 formats should work though. It seems to work fine with my testscript, that streams random music videoclips from youtube.
I use from time to time castnow. It can send any local media or folder with media to chromecast, even URL or torrents as well from the command line. Is written in JS
There is also a desktop app called MkChromecast written in python which is pretty good doing the same.