Yeah, the ADXL202 is an accelerometer but in this case it's measuring the accereration due to gravity. In my evaluations of the part I found it to be quite repeatable. Once the microcontroller was taught where straight and level was it always found it again.

Grab application note AN715 from Microchip:

http://www.microchip.com/1010/suppdoc/appnote/all/an715/958/index.htm

It's interesting stuff.