Take all of your plans, schemos, drawings, sketches, blah blah and mail them to yourself from the post office. You now have a government time stamp on when you created and mastered the idea. If someone steals it they have to prove 100% that they came up with the idea or at least had it in the planning stages before your post dated stamp that proves when you had the idea.
Just keep the unopened letter in your drawer and if shit goes left pop it out and they'll open it in court. You won't automatically "win" per se but it'll go a long way towards proving ownership of the IP. And then you can sue in a different court for them making money from your idea once you prove you came up with it first.