I'm still patiently waiting for BMW to update the button on the steering wheel to activate Siri.
Until that happens I'm researching alternatives. One I discovered today is this product,
http://www.drivewithsiri.com. Its basically is a garage door opener sized home button that activates Siri. MSRP is $79.00 (which is a bit much IMO) but I may order one just to give it a try.
I think this is a neat alternative for those who don't keep their phone in their front pocket.