Ingeniously simple, the Rolling Pin Ruler. Next time your baking and the recipe says roll out 15inch squares of pastry, instead of just guessing you can measure it with the rolling pin. Can be used to measure up to 12 inches (30cm).
It’s a good job it’s labeled rolling pin or visitors might mistake for something else (though I’ve never seen one with measurements on the side). Available from Drink Stuff as drinking and burning baking are so closely connected.