Paper cup iambic paddles
One day in a meeting I was drinking tea from a paper cup. Suddenly I realized that my fingers had started playing with the cup handles as if they were iambic paddles.
From idea to reality: All you need is two paper clips and a piece of aluminium tape. See the pictures for construction details (click to enlarge them if necessary). An empty key is very unstable due to its light weight, so before keying fill it with something drinkable.