voice over and gps

Hi everyone! I am a very recently user of an iphone 4s, my first ios product. I love voice over and i would like to use all the benefits of the phone. One of them is gps; i know that voice over doesn't speak with igo or navigon, the most used softwares in Romania, where i live. Could you give me a solution to have a very good map and in the same time to be spoken by the voice over? Thank you very much anticipately! Best wishes, Tibi!