Comment Better go with local companies. (Score 1) 262
If your device contains patentable ideas, I would really encourage you not to have someone in China or elsewhere out of country do it for you, otherwise any IP you may have in it may well be gone right away.
It is definitely the better idea to look up local electronics design and assembly companies and have them do the work for you. Not only are they going to be in the same timezone as you are and will generally turn out to be much more responsive with regards to modifications and problems than someone abroad.
Especially if you go with small businesses, your project is going to be much more relevant to them in turns of money in comparison to their total earnings, so you will be much more important to them than you would be to a large design and assembly company.
Just look up a few in the yellow pages, have a chat with them and go with the one(s) that you feel you are on the same "wavelength" on.
Also, you can sign Non Disclosure Agreements with them, which are much easier to enforce because only your local laws apply.