I happen to have one of these, and am *considering* diving in to see if I can integrate this with bwi(4). If you're already working on this, or if you have worked on it in the the past, please let me know; I would hate to duplicate your efforts.
While I have not yet begun scoping the technical requirements, a bit of Googling indicates that Broadcom made their applicable 802.11 Linux driver open source in September 2010. That may be a starting place....Or not. :) Thanks!