What is it?
Cast is an app that works together with a Raspberry Pi to be a Chromecast alternative.
How can I use it?
You can download the apk here
In addition you need to install youtube-dl in your Raspberry Pi:
sudo curl -L https://yt-dl.org/downloads/latest/youtube-dl -o /usr/local/bin/youtube-dl sudo chmod a+rx /usr/local/bin/youtube-dl