My sister bought my son an inexpensive MP3 player when he was six. She got it for Christmas and loaded it up with all his favorite songs and a few that she thought he might like. Since it wasn't that expensive, it wouldn't have been a huge deal if it broke. But the rule was he could have it around the house or in the car, but couldn't take it with him to friend's houses or, obviously, school.
It was a great way to introduce him to music. My husband would change out some of the songs or load new music once a week or so. My son could pick out new music for purchase as a reward for things.
I think the appropriateness of the age has everything to do with how involved adults would like to be.