Guess it's one of those 3rd screen things, sit back, watch the game, and make bets on your ipad. Not sure it's safe for the pocketbook, or the ipad if you spill beer on it.
I think it's both that, and the overall convenience of mobile. In the past, you would think, "hey, I can bet on that!" and then you usually aren't near a computer (or a casino). Now you always have your phone with you