I don't think there's an added expense to have a tracker that stores music. But, your best bet would be to contact your wireless carrier to check that. And they usually connect to your phone by a blue tooth connection.
Here is a link to Fitbit's products. You can compare them. I did a quick look and didn't see any that can store music:
Hey everyone. I've been thinking about getting a tracker and I've read some stuff on the good, bad and ugly but I still can't decided. Currently I have an Iphone but once it needs replacing I'll likely go back to Android (I'm not fussy but my bf is and the phone is his old one since he hated my Android). Anyhow, I'm debating on a Fitbit v. Apple Watch v. Garmin.
I like the idea of being able to listen to music/pod casts when I walk and the heart tracker but not necessary. It would be nice if my Iphone could connect to it so I don't have to carry both around, however if that's an added expense to my phone bill forget it! I don't want it to make calls necessarily but I would like it to transfer my stuff to spark and/or to my phone. Being able to track distance would be a bonus. Lastly, I like to swim so water proof is a must. Can a Fitbit do all this or do I need to get an Apple watch, and if so, is there a monthly added on to my phone bill?? That's the biggest negative since I pay a fortune as it is.