Does anybody know if the Droid is capable of pushing audio out via USB like the G1 does with the mini usb?
I am not sure if this is a hardware or software solution (or both). Furthermore, I am not even sure its possible with the Droid... I have no idea how it works on the G1, I just know it does, lol.
Here's the skinny on these issues.. I don't know everything about the DROID's capabilities (I have one, sure enough).
USB is a master/slave protocol... you need a master device, like your PC, and a slave device, like a USB stick. Masters can't talk to masters, slaves can't talk to slaves. Almost.
In USB 2.0, they added a thing called USB on-the-go, which allows a device to do both, by detection what the "other guy" is doing, then do the other thing. Some devices support this. I have a camcorder that can back itself up to a USB storage device, but also hooks up to a PC as a storage device itself.
In addition to the hardware, you need device drivers on the target device. A device might well support USB on-the-go, but if it doesn't know about storage device or keyboard or mice or whatever, it can't support them.
I don't know of any evidence that the DROID supports on-the-go. To be able to "push" audio over USB, it would have to be able to present itself as a USB audio device. However, there are many USB masters (PCs, my Pioneer car GPS device) that know how to pull audio from USB storage devices. I haven't tried it, but there's a good chance my GPS could use my DROID as an audio source this way. These things are subject to other issues... for example, does your USB master look everywhere on the USB storage device or media, or is it expecting this to be in a certain location? A PC, my PS3, etc. can definitely work with the DROID this way.
The other main way to get audio out easily is via Bluetooth. The DROID does support the AD2P (Advanced Audio Distribution Protocol) profile, for talking to music quality headphones It is compressed, and by default uses an encoding called SCP, which is simpler than MP3 but kind of the same idea. The protocol handshakes with your headphones, and supports direct distribution of encoded audio without re-compressing if your headphones support it, in MPEG, AAC, and ATRAC formats.
Of course, like every Bluetooth phone, it also supports the HSP "headset" protocol, which is monophonic low-quality audio in one direction, voice in the other direction, each at 64kb/s using the very low complexity CVSD compression, or straight PCM audio (8-bit samples at 8kHz).