If you want to be secure, you need to talk to a decent attorney. You will need to patent or copyright it to be fully protected, I think (ask a real attorney). You can have the company sign a non-disclosure agreement, but they are often hard to get signed since the company will be afraid that you really have nothing new, and then might sue them for something they already have. Pitching companies is easy – all you need is a decent proposal and basic sales skills. Protecting your idea is a whole different story. I would get decent legal help before I make that first sales call.