That's a common fear, but you are better off putting that aside and just going for it. Instead of worrying about someone taking your idea, have any manufacturer, pattern maker, etc sign an NDA, and move forward with your idea. And most importantly, work with people you can trust. Even if your ide...
If you have your CAD design done, you can get it printed in plastic first using inexpensive printers at 3DHubs for example. Do tweaks to the design and reprint. This can't cost more than $5 or so per print. Once you're happy you can then send your design to shapeways or i.materialise to be prin...