the emitter voltage tells you what the LED voltage is when on, and you use this to set the current... (VCC - emmiter voltage) / current desired through LED = Resistor Value... if you use current in mA, R will be in Kohms.
The difference between the LASER and IR diodes is that the laser light will go further without spreading (which causes signal loss) because it is coherent light. We built a Pitch-N-Catch® machine for the Royals one year. It was a box with a 3' x 3' opening placed on home plate that the pitchers would pitch into, and it would display the zone and speed of the pitch (it would also give indication of ball or strike). We used IR and thus had to have lenses on both the emitter and receiver sides. You must lay your parts down and test how far you can detect. I don't remember how far we had spaced each sensor from the other, but we had to detect something the size of a baseball, so it wasn't much larger than the diameter of a baseball. Also, we alternated transmit/recieve pairs for more isolation.
The biggest problem you're going to have, and I don't know how they get away from this in their laser pad unless they multiplex power to the emitters one at a time and now that I think about it that won't work either... anyway, the problem you're going to have is with multiple break points. If you put both feet down, you won't be able to tell which X break goes with which Y break... ex:
Let's say you set up your infrared like the BELOW. ok, one foot goes down, no problem, one broken x and one broken y.... but with two feet placed, you'll have two broken x's and 2 broken y's, and won't know which x goes with which y.... #1 gives the same output as #2
Mike