[cogman10]

Background helps a lot, but if your things are relatively the same color, it's pretty easy to just filter out anything not within that color range and look for circles, even with an inconsistent background (though, admittedly it's harder).

That's effectively what I did with the ball tracking. I had a red ball and filtered out everything that wasn't roughly that shade. Certainly someone could have messed with me by wandering into frame with a red shirt :D