I'd like to know more about this aswell. I've installed the MyAudi app on my phone but a lot of the advertised features are not present. Apparently, you need to input a 10 digit code into the MMI to activate some of the features and this 10 digit code comes on a plastic key fob that should be given to you when you buy the car. Mine didn't have this code with the keys so I am currently asking my dealer to obtain the code for me, they said they can order it, will take about 10 days.
However, like you say, I think some of the features are not available on the "3 series" anyway.