A friend of mine, is using android tablet on his car. no front end. just a madia player called "black player"
He had the same problem as you, but he found out that you can solve this problem in 2 steps.
1) find media controll widgets that seem nice to you
2) then there is an app (dont remember name but can ask), that makes any widget, a presistent one !
but this way you will have the controlls, even when inside the front end... !