from my experience with cheap chinese mp3 players under $10 bux, the common issue is the quality of the lithium battery. It will be fine for about a week, but a few recharges later the battery ceases to hold a sufficient charge.
I was looking to listen to songs while jogging or doing other sport, but I have Bluetooth sport set (plantronic beat fit - $90) already. not possible to carry my 5.5" phone, so my solution:
galaxy gear ($99), put songs on it and then wear the gear and Bluetooth set.
expensive stuffs, yeah.
I currently use a wired set and carry my phone while jogging. I also use runkeeper or Garmin fit to track my runs.
I was looking at getting a GPS watch so I can leave the phone at home but then I need music as I really don't enjoy jogging at all so music distracts me.
Sony has an mp3 Walkman but it's $100.
Will wait and see what my $4 item goes like. Maybe I can change the battery if it looses charge quickly.
I brought a very similar pair off COTD a few years back. Couldn't get them to pair with anything..
had one loooong time ago if I remember correctly, it hurts my ear after few minutes usage. probably due to low quality of the plastic