Well, the requirements are getting looser. 
For sure an Arduino can read values up do 150mV. As I told you before, in theory, from 0 to 150 mV, the Analogic Port of the Arduino can detect aprox. 30 different states/steps, each one 4.9 mV far from each other.
I would try mounting the circuit that I mentioned (which is trully naive, since I´m not an expert in electronics) and see what it can get in the Serial Monitor. If you´re ok with the readings, then you can go ahead and do all the LED stuff of even recording the values in a data logger.