Ok, I guess this is going to be off topic and TMI
Jelly Bean was touted as having support for audio streaming via usb. Apparently you must have devices that support Google's format.
Normally, usb audio streaming via usb is digital DATA, as opposed to analog audio (like you get out of the headphone jack).
This means that data is streamed into *something* that has a DAC (digital/analog conversion) chip.
In the audiophile world, high res digital audio is streamed from a computer (preferably at a high bit rate) using a capable software player, to an external DAC, (bypassing the crappy one on the sound card, or phone) which is then hooked to an amp (speaker or headphone amp) with normal stereo cables.
All of the usb ports that I have seen in car audio stuff just use the usb port to mount external storage devices, like a flash drive, or maybe even a hard drive (with a file/directory limit).
A car audio system has to have a DAC if it plays CDs or mp3s, so it shouldn't be difficult to manufacture that capability.
Here is some info on a digital audio streaming capable player for android.
USBAudioRecorderPRO
Here is some info on results with various devices
Android phones and USB DACs - Page 150
I have been REALLY hoping that Google could get standard support into android and get the proper hardware into a device (moto??) so we could use our phones for high quality audio...