Iphone playing Spotify or Pandora through car audio?

[X14Halo]

Whenever I plug my iPhone 4 into my car stereo, it automatically goes into "iPod mode" and will only play music on my iPhone. I can text and use apps while in this mode, but how would I get it to use the audio from apps like pandora or spotify?

 

[iCrank]

Whenever I plug my iPhone 4 into my car stereo, it automatically goes into "iPod mode" and will only play music on my iPhone. I can text and use apps while in this mode, but how would I get it to use the audio from apps like pandora or spotify?

Good question. I have the pioneer app that does that for my suv. Don't know of any others