Check out this very inventive use for a cam-based wave machine…
From the video description:
The Cache Machine is a kinetic sculpture that adds rhythm and irony to the tradition of hiding coins in a safe place. Taking its form language from the industrial heritage of the North of England and obsolete scientific apparatus, the machine comes to life when a coin is inserted. This coin travels along a mechanically generated transverse wave that is activated by a poetic system of cams and levers. Upon reaching the end the coin is deposited, with a satisfying clang, into an eagerly awaiting collection vessel.
See more clever things by Martin Smith on his web site.