Yes, this is the one MAJOR feature that I wish was on this phone. However, I doubt that an app is going to be the fix for it as it is something that has yet to be coded into the kernel itself. And FYI, the kernel is way below the actual firmware version or any updates thereof, as far as I understand it.
There was an app that I can't remember the name of because they wanted a boatload of money for it, and all it did was enable the use of your camera button to bring up the phone dialer, yet it still did not switch to your BT headset until after the call was made. What a waste, IMHO.