It's a pity there aren't any open source video recorders - I might be able to program mine if I knew how it worked :)
If the software was released under the GPL the OEM's would be legally required to ship the source code with the unit. Any improvements people make to that code could be collected by you for inclusion into your product (I doubt if OEM's would go down that road).
IMHO you are not in competition with the big players anyway, certainly not at the moment. In the future the large Japanese firms will start producing mainstream MP3 players - they've already started. The only thing differentiating you from any of them will be features and quality. Quality is an easy one - you only produce small numbers of units and I am sure (from what I have seen) that quality control is high. The best wasy to make the software better is to get all those who want to be involved the chance to be involved - open source.
In Australia, there is a local manufacturer of amplifiers branded ME. They are a small company in Sydney producing small numbers. Every until that goes out the door is personally signed by the owner. The quality, finish and performance is outstanding and as a consequence they have trouble producing enough for the demand. I was lucky to get one. The point here is that they are not competing with the large players and found their market. It's not hard to pull apart an amp to copy the internals - but no one has done it and probably never will. Besides, I doubt if any manufacturer would be interested in tackling the potentially large amount of support needed for such an esoteric item.
But far be it of me to suggest how you should run your company - I'm on the other side of the world !! :)