The is an Irish Halloween tradition based around putting things in cakes:
The Barnbrack Cake: The traditional Halloween cake in Ireland is the barnbrack which is a fruit bread. Each member of the family gets a slice. Great interest is taken in the outcome as there is a piece of rag, a coin and a ring in each cake. If you get the rag then your financial future is doubtful. If you get the coin then you can look forward to a prosperous year. Getting the ring is a sure sign of impending romance or continued happiness.
I also recall having apple tarts as a child with coins (wrapper in tinfoil) in them.
As for the Kinder eggs....don't boarder guards have bigger concerns?