When it comes to music, Music Voice Control is very useful if you have a huge playlist and want to change what's playing. You don't have to browse your big playlist to search for a song that you want to listen. Just speak the song name and your device will start playing that particular song!
Windows operating system is shipped with voice recognition built-in for a few years now. Like most of you, I tried it but it didn't worked very well, and hadn't looked at it since. Microsoft voice dictation requires an expensive mic and takes a long time to set up, and it is not a reliable program for accuracy.
Microsoft recently launched Cortana for Windows mobile 8.1. Siri and Google Now are pretty good vitual personal assistant apps for iOS and Android respectively. Here comes Braina, a very intelligent and useful digital personal assistant software for Windows OS from Brainasoft like Jarvis from Ironman.