Google has a celebrated history of introducing hoax applications on April Fool's Day. Remember "AdSense for Conversations?" It was going to let us display topic-linked ads on inconspicuous screens above our heads as we spoke. Or PigeonRank? Google Romance? How about the one that would let us send e-mails in the past? Google Australia apparently kicked off the hilarity early today with gBall, an overly smart device that "will change Australian rules football as we know it."