Have you ever played with the magic 8 ball? This is similar. Type a yes/no question (e.g. "will I win the lottery?") and press enter. The ball will give you an answer.
Remember that some religions aren't happy with the idea of predicting the future, so if you have, for example, any Muslim students in your class, be aware that this might not be an appropriate activity.
And if you'd like this on a bigger interactive whiteboard, click on this link for the full(er) screen version.