Natal can detect an area of 15 X 20. So you could probably do a good mapping of a tennis court. Would not be 1:1 for size with a real tennis court but neither is the Wii tennis game.
And that would be a pretty good workout right there. Now you add online capabilities and you have a pretty neat little setup there. The only problem with this is that it takes a whole friggen room to play. But I would definitely want to give that a try. Could be used in physical therapy as well.
I will once again mention the Tron disc game from the movie would be an utterly amazing game to play on Natal. And it looks like it could be done rather simply.







