My 2005 E450 Itasca motorhome's stock RV weather band radio has an AUX connector in the back in the back of it that I discovered after removing it from the cab dash. I plugged a short coaxial audio cable into this and brought the end of this cable out to the front where is lays on the engine doghouse cover for convenient access whenever I want to plug an external source of audio into it.
What I usually plug into it is another cable coming from the audio output of my widescreen laptop for watching movies on the laptop with it's sound piped throughout my motorhome using it's built-in surround speakers that are hardwired to the cab radio. The AUX input to the cab radio uses this same hardwiring so that you can route other audio sources into these speakers and then control the audio with the radio's loudness, balance, fade, bass, and treble functions .... very nice.