Iphone 4s not outputting music to bluetooth handsfree kit?

I bought a bluetooth handsfree kit of ebay so i would be able to play music wirelessly to my head unit. The device also functions as a handsfree kit. I'm able to connect to the device without any trouble on my iPhone 4s as well as an iPad and two iPod touches but i'm unable to stream music to it. I can output voice memos and the phone without any trouble but whenever i switch to music and click play the option on the right side of the screen to export to the kit disappears and music plays out of the phone speaker. I thought it might be the kit but they sent me another one and assured me it should work but i'm having the same issue.

I tried connecting my Mac pro and was able to and stream sound from my laptop to the kit. So at this point i'm not sure wether its a issue with the portable devices or the bluetooth kit

I haven't found anything on Google except that the 4S has issues with some bluetooth devices but it should work with the 4 or the iPod touches shouldn't it?
Any tips?

The Bluetooth is most Likly not compatable

Handsfree kits arnt really made to listen to music so it normally doesn't play or sometimes does real qietly if you want to listen to music youll have to but a pair of bluetooth head phones like a pair of Dr. Dre's.