I have been involved in over 40 technology dependent startups. The best protection is dealing with reputable people. A practical management solution is to farm out manufacturing of the individual components to more than one (maybe not "multiple") manufacturer. You can protect yourself under a contract as well. The second best protection is to spend money on an IP lawyer and get a patent, or patents, to protect the idea. You can also copyright the plans and the schematics. All of this of course assumes that you have money to defend the patent and to sue people who break the contracts. If you would like to discuss this further, please feel free to get in touch.