Note that this is why standalone MP3 players have been unable to garner marketshare in Japan: everyone's cell phones were already their mp3 player (and they bought the music OTA via their phone, to boot). As is, the days of standalone music players are likely numbered.
What about the ipod classic? For the moment this gives a lot bigger capacity than you can get with a phone and for a lot cheaper price. Plus it's very straight forward to play music.
Although if you were to only carry around one device it would be a phone, just personally everywhere I go that I would usually want a mp3 player I carry a bag making carrying two devices a non issue.
