I`m not too knowledgeable about building prototypes and what not, but consider filing for a patent and then going to elance to hire an engineer to build your prototype.
You might also consider filing for a "provisional patent" and contact some of the bigger companies in the industry on your idea. If they like it, they will pay you royalties based on your idea.
Here are two sites you can refer to:inventright.com
(this site offers a package on the whole process of inventing and patenting. It comes highly recommended by author Tim Ferriss.)guthyrenker.com
(this is more for after you have put together the product, but still somewhere you can look one you want to sell it)
MattThomas2/6/2009 5:39 PM
Motivation for Entrepreneurs