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!