Am testing a new to me app called AUTOIPTV that will allow you to play various IPTV streamed radio stations over your android auto radio. There are lots of audio only channels you may subscribe to with a provider.
Just not sure how they provider will react to changing IP address on the data channel of a smart phone.
One thing did notice is that there seems to not be a mechanism to display ARTIST and SONG TITLE with a stream. Most of the online streaming stations that run via other apps all will display information.