I propose you to make some empirical studies on that.
I'm on the development of an application and I want to share the GPS position with other mobile phones. Well.. I have a thread that get the current position of the mobile phone every 5 seconds and send a request to
http://localhost/database/insert_gps.php
That's just an intro to propose my idea.
I think you could make some modifications to your application, and save the values in a database in your mobile phone using PAMP. You will be able to study how long did the battery lived, and which vas the battery level in each moment.
Then just divide the time in sections and check which vas the value at each moment.
If you do this study several times, and with the conditions of just running your Python application and PAMP, you will get a study based criteria to determine if you have 50% of the battery according to the values, even you have all the bars printed on the screen.
I can provide you some code in PHP to solve some problems in the INSERTs, as it seems that MySQL crashes after a table file is bigger that some KBs.
Hope this idea helps
didacgil9@gmail.com