It unlocks an alley(very small area) where you can get the "Nutrition Specs" glasses.
There is even a trophy to unlock : you have to reveal a secret object. I still don't know what it is!
I have tried the glasses in the restaurant and it analyses the food, the aquarium, the pie, Stinky. It gives the composition of the element you analyse. It's pretty fun. There is some addditional dialogue.
I'm glad I bought it on PS3.
For those wondering how to get this on PC, I'm sure Telltale will unlock it at some point. Remember ToMI when they unlocked a special mode? I'm sure they will do the same.