GameSlam gives baseball fans a deeper way to play along with their favorite team in real time than fantasy sports.

Baseball is a team sport, but for fans of the major leagues, there's never been a good way to play along in real time.

Until now that is, say the creators of GameSlam, a real-time social predictive baseball game that allows fans to get in on the fun even as the balls and strikes are being thrown and the home runs are clearing the fences.

For years, baseball aficionados have been able to take part in Major League Baseball by joining a fantasy league. And there are 10 million people in leagues like this, as well as 20 million more playing fantasy football. But to the GameSlam founders, that option lacks one key element of the fun: competing against friends and others while the ballplayers are still on the field.

But with GameSlam, which is launching officially today, they say, players can enjoy the statistical ups and downs of fantasy baseball at the same time as they share in the social experience of watching a game with friends.

It works like this. Players can get in on the game via GameSlam's iPhone or iPad apps, or on their computers, and start competing with their friends to see who makes better predictions, either about the outcome of a full game, or about individual pitches or plays. Or both.

Logging in, players will see the GameSlam interface, which, among other elements, features a gamecast that is synced to whatever real-time game they're watching live on their TV, meaning that as the real-life action progresses on the field, GameSlam is delivering the same action--just digitally. It doesn't work with games saved on a digital video recorder.

Being a competitive game, the system starts each player off with 10,000 points, and then adds to, or subtracts from, that number depending on how their predictions turn out. Guess correctly that a player will strike out, you gain more points. Get it wrong, and points are deducted.

Casual players may choose to stick to predicting who will win and then grab a beer and sit back with their friends to watch on TV, content to see their point totals rise or fall depending on the way the game turns out. More dedicated players will dive in and make predictions about myriad plays during the game, putting themselves in position to rack up a great deal more points, assuming they're predicting well.

While GameSlam works well for friends who may be watching a game together on TV, it also works for those who are remote. And, because it's a competition, players can join leagues--of 100 people--and see how they stack up over the course of a number of games. Winners of the various leagues can end up with small prizes, or credit towards premium features.

GameSlam is free to play, and the company behind it hopes to make money through a series of virtual goods and premium options. For example, if players don't want to compete against strangers, they can upgrade to premium and play in leagues only against their friends.

Is it fun It's too early to tell. The idea seems compelling, but in order to work, it will have to be simple and easy for the casual users, while giving serious fans enough to keep them occupied. The company clearly thinks that its reliance on a microtransactions business model will make it profitable quickly, but without a critical mass of players, it's hard to see why anyone will pay. Still, that's no different from many other services, so it would seem that the devil is in the details.