I have been looking for alternative hardware options to help with miniturization. Also to help with production costs attempting to re-use the same components. I came across a bluetooth bee style module with an arduino built into the same board.
That will cut down on space requirements quite a bit. The header pins would allow for a secondary board of the same shape to plug right in, which could hold voltage regulators for the bike module, and could hold the LiPo charging circuit and a surface mount headphone jack or two for the jacket wiring connections on the jacket module.