1. A processor-implemented method for detecting motion in a 3-D depth camera, comprising the processor-implemented steps of: obtaining acceleration readings in x-, y- and z-axes from a three-axis accelerometer in the 3-D depth camera at successive time points, and for each time point: obtaining short and long term running averages of the acceleration readings in each axis of the x-, y- and z-axes; obtaining differences between the short and long term running averages of the acceleration readings for each axis of the x-, y- and z-axes; obtaining absolute values of the differences for each axis of the x-, y- and z-axes; obtaining a sum based on the absolute values; determining if the sum exceeds a threshold level; if the sum exceeds the threshold level, providing an indication that movement of the 3-D depth camera is detected; and if the sum does not exceed the threshold level, providing an indication that movement of the 3-D depth camera is not detected.