How to get soundwave/visualization data from the microphone?

I haven't noticed a way of getting more than one value without capturing the sound first. You could try with the Audio record library and capture on a separate thread.

I don't know how well the displaying would keep up, as with your other question on the Audio record thread, you'd probably have to average the values in some way to get the best representation.

You may be able to find some relevant information on a search engine, it's would be a generic display solution for sound files.

Displaying isnt the problem, I have API for that.
It's getting the data, how would I do that?

We have two threads going round the same question, have you looked at the sample code that is available with the AudioRecord library?