Here is a terrific example, from the folks at NTD, of what you can do with some cardboard, superglue, hot-melt, a handful of plastic syringes and some fish tank air line. This video can also be viewed in much higher resolution by clicking HERE
Rapid Prototyping is an extremely useful tool in the early stages of concept development. Doing something like this might uncover a latent flaw in an idea which wouldn't otherwise surface until much later if using a top-down design process.
