If you need VoIP application that is portable, can be bring anywhere, I suggest you to use this Skype 5 beta portable edition for Windows. This is unofficial portable edition of Skype. You can download this Skype portable from the link provided below this post.
I have a scenario in which i am recording audio in background. Now when Skype call comes i want to release the hold of mic and let Skype do its job. To get the Skype event i am using AudioManager.MODE_IN_COMMUNICATION event. But this event doesn't seem to be working and releasing mic because of which two parties on Skype can't speak to each other.