Could you create a robotic baseball outfielder using today’s technology, if it didn’t have to be a humanoid-shaped robot?

In other words, could you take a moving platform like a car or Segway base, outfit it with sufficient visual and tracking devices and some kind of armature, and create a mechanism that was capable of: i) identifying the trajectory of a batted ball; ii) moving to the location where it would land; and iii) catching the ball in a standard glove?

I would say definitely yes. Jean-Jacques Slotine has video on his webpage showing his robot arm catching balls and paper airplanes.  He says that by the time they were done with it, it was tough to throw a ball that the robot wouldn’t catch.  That was back in 1995.  Back then they used several computers operating in parallel, but the same code would run on a single PC today.

It would be even easier if the robot were allowed to use some form of radar or laser scanner to acquire and track the ball. (You might have to worry about fans with jamming devices.) But I think it would still be feasible even if the robot were restricted to cameras analogous to human vision. The ball is a nice white moving point against the grass or sky. The other players and umpires are conveniently color-coded blobs. Bottom line: a baseball field is an extremely controlled, predictable environment, just the sort of place where a robot could easily flourish.