BuddyPress.org

I use google analytics for BP as well as my regular WP sites. However, I still end up using statpress plugins for my regular WP sites, I guess because they are right there in your dashboard and give immediate uptodate information.

I agree that the overall statistics for statpress are always higher than google analytics (I actually have no idea which is accurate) but for checking if your site has had any activity in the past few hours, there is no better than statpress.