Twin #2 already made his plea (and re-emphasized it just a few days ago), but it has become so obviously necessary that another forceful argument for it is not overkill. I am, of course, talking about instant replay.
The first question that must be addressed is: does baseball need it? After this year's playoffs, I think that answer is a resounding yes. The missed calls are piling up, and the hits just keep on coming as yet another call was missed in the game going on right now. Joe Mauer's missed double headlines the group (in my opinion) but the list extends for quite a while considering the small number of games. If this amount of mistakes doesn't bother you, then you might as well stop reading the this, and also rethink what is important in baseball.
How would replay work logistically, though? Some people cite the NFL's lengthy delays and worry that the same thing will happen in baseball, making an already slow game droll on for hours. I, however, point to college football, which has a much better system. It's also essentially the same as what Twin #2 proposed in his post.
Simply add an extra umpire in a replay booth for every game. I don't think he should be a member of the umpiring crew who rotates to the other positions, but that's a minor detail. If a questionable call arises, he simply sends a signal to the home plate umpire, who calls time and waits for a decision to be made. There wouldn't be a hard and fast rule, but within about 30 seconds the replay ump would have to make his decision. With the time spent tossing the ball around the infield, strolling to the plate, etc., I think it would be barely noticeable. And if he can't decide in that amount of time, then the call on the field stands.
Think about some of the plays that have happened in the postseason. Would they take more than 10 seconds to overturn? This system would be efficient and get calls right and eliminate the need for silly arguments between managers and umpires, while talking no more time. And I'm sorry, but if you would miss that, I'm not sure you're watching baseball for the right reasons.
Of course, if the ruling is reversed, there's a good chance judgment calls will need to be made regarding where baserunners should be. That will add a little time, and it may prove easiest to have the replay umpire make those decisions, which would mean he would be given more time for his decision. There are already rules in place for cases where umps have to decide what would have happened--fan interference, for example--and those rules can be extended to include replay.
The only real drawback, in my opinion, is something that can't be explained simply. Think of what happens in football when a touchdown is scored. If you're like me, first you scan the field (or TV screen) for flags, before considering, if the play was close, whether it might be challenged and then overturned. Think of basketball. If a player scores at the buzzer, there is always an elaborate examination to determine whether he got the shot off in time or if there should be some time left on the clock.
In baseball, however, as soon as a team scores, you can experience unrestrained jubilation. You know there is no way that that run is coming off the board. Unfortunately, the immediacy and finality of that initial decision is what causes so many errors to occur. With that in mind, it wasn't easy at first for me to commit to replay, but the postseason has made it so much easier. The number of obvious mistakes has swayed me to become an unwavering supporter of a much more extended replay system.
And, honestly, don't you think the umpires would support it at this point? If you were an umpire, wouldn't you?