Today I've performed very simple experiment to see if my code and assumptions about accelerometer are correct so far. I have written a script to show "live" value of tilt angle of PyBoard (angle between Z-axis and vertical): calibration_util.py
Today I've borrowed my fiancee's protractor and assuming that:
a) my desk is leveled enough
b) my hands are steady enough
I just aligned the board with marks on protractor every 10 degrees. Everything seems to be correct.
Of course angle is just a beginning. I'm yet to calibrate the meter to translate degrees to flow speed and so far I don't have a good idea how to do it reliably and with reasonable effort.