"The Physics Teacher's" "iPhysicsLabs" column has been dedicated to the implementation of smartphones in instructional physics labs as data collection devices. In order to understand any data set, however, one should first understand how it is obtained. This concern regarding the inclusion of smartphones in lab activities has arisen in response to the creation of this column1 as well as to a paper in a recent issue of "Physics Today." The majority of the labs featured in the "iPhysicsLabs" column to date make use of the internal accelerometer, common to nearly all smartphones on the market today. In order to glean meaningful conclusions from their data, students should first understand how the sensor works, as was pointed out in the first article to be featured in that column. We attempt to elucidate this "iBlackBox" using a simple ball-and-spring model.