How to use the sensor next to the front camera on a smartphone/tablet?

Question

Android

Does it pick up movement? Or just can determine the degree of illumination?
Where can I read how to programmatically parse data from the sensor, if possible? And is it not prohibited by Google in the market? Although, this is just a completely meaningless and stupid assumption.
Unfortunately, I googled only a cookie with butter.

Answer 1

Everything related to the sensors is here
. See Summary for all available readings.