The accessory may not be a MUST have but the splitter for dual headphones is really nice.  The regular headphones are not much either for quality nor do I need the thermometer or the end cap but it is a really nice kit and I enjoy the case for it all.  Mainly the splitter for me made this purchase worthwile since I do a lot of trips where I could share my playlists!  The only reason I gave it 4 vice 5 stars, is the quality of the included headphones