If you are talking about using voice recognition in your code somehow, then you can use it with the help of SpeechRecognizer class(http://developer.android.com/reference/android/speech/SpeechRecognizer.html) and RecognizerIntent. But you can only use the currently existing functionality to some extent only. About the confusion as to whether it lies in device or not, try using your Voice Recognition after turning off internet on your phone. It wont work.
You can also look into API Demos for some example: sdk\samples\android-10\ApiDemos\src\com\example\android\apis\app\VoiceRecognition.java