We're in the process of adopting a cat from the NAWT, who sell this in their shop. The member of staff who matched us with the cat uses this with her cat at home.
You divide the day's portion of dried food into five 'mice' and then place/hide them where your cat will hopefully find them.
Pros: Mimics hunting behaviour, prevents cats from rushing their eating, keeps them occupied.
Cons: Expensive, more of a faff for the human, what if the cat is too lazy/dippy to find the food?
Has anyone actually tried using this?