I've not done this on an android (new to android development and this forum actually), but I wanted to share my idea of how I'd attain volumes from the microphone(s).
Various links for gathering audio:
http://developer.android.com/guide/topi ... index.html
http://developer.android.com/reference/ ... order.html
http://developer.android.com/reference/ ... ecord.html
Concerning volume, I guess you can pick some levels for arbitrary volume granularity as may be inferred from the first few paragraphs here:
http://www.ypass.net/blog/2010/01/pcm-a ... e-control/
So you could have some algorithm that over a certain amount of time would take the absolute values (remove negatives), get the average of those numbers (with or without outliers, I don't know) then compare them to some volume cutoff values you have selected. This could run in the background and have overlapping samples over time.
You may find going with the median is better for your purposes.
Alternatively, you could have it return a positive verification once a certain level has been reached in the raw pcm values (probably absolute values unless you're particular).