These ideas have been done forever. It could work, but has limits. The _best_ and _safest_ way is full registry. But you have legal copyright (notice the spelling) as soon as you take the idea out of your head and make a fixed form. Proving it is another matter. It isn't that expensive to file with the LOC (or whichever national registry fits your geographic circumstances).
I'm going to lock this thread, because the concept has been discussed ad nauseum on this and many other forums.