If you're looking to create mobile applications (when I hear "mobile" I think cell phones, PDAs, etc.), then you will need a J2ME SDK (Java 2 Mobile Edition), and a Java-enabled device. Finding a Java-enabled device shouldn't be too hard these days.
As for the voice recognition and such, you may have to look into, and concern yourself, with Java sound APIs and look into voice-recog. algorithms.
And, as mentioned before, it's all only a short Google search away.
Well to create a mobile application u will need a
J2ME SDK & to create a voice regognition Application You will need a SAPI ( Speech API ) SDK.
There on you need to integrate ur Speec application into ur mobile application to do any operations u need.