1. An apparatus for determining whether a user intends to provide an input using an image of a control cell appearing on a surface, comprising: a first camera to capture a first set of two or more images of the surface, each captured image including the control cell; and a digital processor to determine whether first, second, and third conditions are true, the first condition being that a count of pixels classified as skin color within a captured control cell is not be less than a predefined threshold skin-color-pixel count value, the captured control cell having a location substantially coinciding with the image of the control cell appearing on the surface, assigning a numerically ascending index number to each pixel location along a target row of continuous pixel locations traversing the captured control cell and summing select index numbers to establish the second condition, the second condition being that the pixels classified as skin color persist for at least a particular time period, the third condition being that the pixels classified as skin color have a first shape, and to provide a signal indicative of an intent of a user to provide an input if the each of the first, second, and third conditions are true; wherein determination of said third condition includes bifurcating the captured control cell into two regions abutting along a linear divide, the two abutting regions defining a first region including all pixels classified as finger-nail color and a second region excluding all pixels classified as finger-nail color, determining a first width span, i.e. W 1 , of pixels classified as skin color in the second region along the linear divide that abuts the first region, the captured control cell having a linear edge parallel to the linear divide, the linear edge being a second side of the second region opposite the linear divide, and determining a second width span, i.e. W 2 , of pixels classified as skin color in the second region along the second side of the second region, and determining that the third condition is true if an absolute value of a difference of W 1 and W 2 is less than a predefined margin value.