I have been looking for something like this forever! http://www.drivewithsiri.com
For those with an iPhone, iPad or touch, this is your new must have if your state has the "hands free" law while driving (like California).
NOW!!! I plan on ordering this bad boy and modding it to fit in the steering wheel (right hand side) in the nice little black bar above the cruise control buttons...
Only down side, its battery powered and has to be changed every 6-12 months unless I find a way to hard wire it, but doubt it since getting wires past the clock spring may be difficult.