Well, iHeartRadio is a popular radio station app on iPhones and smart phones but I think it sucks compared to TuneInRadio. It has like 75,000 radio stations from all over the world.
RadioPup and Pandora(I switch between the two). Both are FREE, and I have a Jabra blue tooth device in my truck with charger for my phone, I just stream these apps to my radio via my Jabra and it is awesome!!!