Haven't seen any. I just use the iPod in the phone, and switch as needed. Now that you mention it, of course I will now have to go looking!
[edit] and here;s something. Not a freebie but it looks OK. I will keep using the iPod though.
https://itunes.apple.com/au/app/sche...520078248?mt=8
and another.. cheaper..
https://itunes.apple.com/au/app/audi...436610163?mt=8