If you have a Series 3, 4 or 5 Apple Watch then you will be able to use the iHeartRadio app independent of your mobile devices.

Unfortunately, Series 1 and 2 Apple Watches do not have enough memory to work independently and the app will work as a controller instead, playing audio from your mobile device.

Note: Your Apple Watch will also need to have Watch OS 6.2 or higher installed in order to use the iHeartRadio app.