AudioControl is a way to control all your audio devices (Sonos, AirPlay, Bluetooth and Chromecast (Audio).
iOS is great, but I don't really like it when it comes to control Audio devices. For example: You have to control Bluetooth devices in the Settings app, AirPlay in Control Center etc. With AudioControl you're able to control all those devices in one app. That's much easier!
How it works
First, you can add streaming services like Spotify and Apple Music, then select wich speakers you want to add, and you're ready to use it.