There are plenty of VIs that are designed to send and receive data and/or digital signals. LabVIEW includes several example VIs on how to communicate with hardware. You may want to look at this other forum thread that has examples and a description of the hardware set up.
How to find moving object/target displacement (how much X, how much Y) using a USB camera in an acquired set of images?: http://forums.ni.com/t5/Machine-Vision/How-to-find-moving-object-target-displacement-how-much-X-how/...