I took the time to look at (I think) every page of your site and some of your patents. You really have been a warrior out there. I believe that you do need to start manufacturing overseas to protect your product. If your product is high priced it can make a juicy target for someone to knock-off. The best way to protect yourself is to take away their perceived margin they`ll receive when they go after the door butler.
It wasn`t clear to me if your would keep selling the doorbutler yourself while the OEM guys sold under a different name, or would the OEM mfg take over the entire brand.
The chances of out-right fraud, say in taiwan or china, is actually quite low. I have never met anyone who has seen this happen. It`s when people slowly get into financial trouble that things get interesting.
As to how do i monitor?
i would be very interested in tracking the physical object. Auditing the books might just get lost in translation. Literally. I would go with a manufacturing inspection
agency at the factory. Say in China. Start this when relations are good. Your inspections would be unannounced and mainly center around the loading of containers. The goal here is to get a general idea of the numbers leaving the building. If things seem to turn sour ... then you can up the inspections for every container loaded. Simply the idea that you can do this with an e-mail to Hong Kong can be quite a reminder.
The real question I would be asking (and you might know the answer
Does this OEM have the ability to distribute. Do you have the confidence in them to sell this product world wide? Will they defend your product from knock-offs the same way you would, or will they just get bored, and move on to the next product, and sort of half heartedly promote your product. Protecting myself here is where all my focus would be.
What an adventure