Stereo, hands down.

I'm not sure if there is yet an Android equivalent to Airplay, but if there is, it should be pursued.

I suspect that bluetooth is not long range enough.

I personally am not interested in a battery pack, but if you could make the power supply internal to the speaker so there is not a wall wart to deal with, that would be appreciated.

Size wise, I'd like something in the M3 range, maybe M2. Maybe both!
I am the Doctor, and THIS... is my SPOON!