How to achieve speech recognition in Unity3d

I am planning to develop a cross-platform speech recognition application using Unity. Basically the app is going to show the text received in different font according to the frequency or other properties of sound.

Can anybody tell me is it possible to get the frequency or volume of sound in mobile device? Also which API i should use to perform speech recognition? The platforms i target are IPhone, IPad and Mac.

Unity doesn’t do speech recognition.AudioListener can give you the output data and also the output spectrum.