I've been to the M Casino. It's not entirely unique, because other casinos are adding the "in game" betting using the same system, which was rolled out initially at the M. This is very different from the normal sports betting because you can bet during the game. Traditional bookmaking will take bets before an event (sometimes even a long time before, for example, the winner of next year's Super Bowl is already a bet you can make in Vegas) but not during it.

I am not sure if a "in game" system ever existing before in Las Vegas casinos to the extent that the M is doing it. The gambling radio shows seem to think it's a novel thing.

I should add that this market (sports gambling) has long had "traders" (people looking to arbitrage games and do other technical actions), "brokers" (people who tell you what to bet on, similar to a stock broker) and "value" players (in the betting case this is guys who look for an imbalance in value, undervalued positions usually caused by too many people betting on one side of a game, similar to Buffet looking for undervalued companies). Recently, I've heard of one of these brokers advertising themselves as an investment group, particularly to the extent that insider trading isn't illegal in gambling (for example, if you have better information on the seriousness of a injury to a key player you have inside information, but instead of it being illegal as it would be in the stock market, it's actively encouraged).

This market is huge. I heard on the radio that Vegas did ~$85 million in bets on the Super Bowl alone.

As a final note, if you don't think you're gambling when you put money into the stock market, then I'm not sure what to tell you.