A free app for Android, by EVOLLY.APP.
The Cast for Chromecast – TV Streaming & Screen Share app is a simple and easy-to-use application that allows you to stream your photos, videos, music, and other media files to your Chromecast device. It works in the same way as other screen mirroring or screen sharing apps, but with one major difference: you don’t need to use your computer or laptop to stream your content.
All you need is an Android device with a working internet connection, and you’re good to go. The app will automatically detect the Chromecast device and connect to it, and you can start using it right away.