Regarding your potential divider, your batteries will last a lot longer if you increase the value of the two resistors so that the current drain is less. I seem to get perfectly useable measurements with 50k or 100k resistors - you might need a small capacitor (say 0.1uF, usually labeled 104) between the analog pin and ground. Bear in mind that because of the uncertainty in the resistor values the accuracy is going to be poor but the repeatability good.
You can further reduce the rate of drain by using a data pin instead of ground - there is quite a long discussion here:
With 50k resistors your current drain will be 40uA through the divider.