Great questions. It works the best from 1-6 feet, so no you don't have to be right in-front of your comp.

The latest version has improved false positive rate where we got one every few hours.

Kinect is overkill for accuracy at this point, so that will not matter.

Lastly, yes camera is on, but app runs locally so no video data ever leaves your computer. Only server component is usual analytics logging.