Some good stuff. I believe Renault was the first to integrate the chimney and T-wing into one unit perhaps as early as 2005. I think Ferrari then picked it up (not coincidentally along with a Renault aero personnel) circa 2006. These dates are rough, I can't remember for sure.
I think the BMW and Renault sidepod developments serve the same purpose as the Macca ones. I'm not sure because I am not a CFD machine but I believe it's to reduce the lateral movement of the air relative to the car and clean up the flow as it heads towards the rear wing and flip-ups in front of the tires. This way it only travels towards the back of the car rather than side to side.
This is all strictly guess work but this type of component seems to be getting more and more common. Ferrari as well now sport a similar looking idea and I think Honda sports a crescent shaped element. They all seem to originate at the front 'corner' of the sidepod. My thought is that as the air hits this perpendicular surface it becomes more turbulent and these devices help to keep that under control. Macca's look to be the most extensive by far.
http://www.f1technical.net/development/116