Contacting a patent office sounds like good advice. I would also consider recording your invention somehow, like with proofofexistence.com--maybe without being too specific so someone else could replicate what you have done. That way, there's a record of it with a timestamp showing you created someting before any competitor tries to do it. That's just a thought; you should probably so keep looking and thinking.
videotape to a flash drive and mail it to yourself.
This wouldn't really stand up in court. Can easily be tampered with. I'd just try find your countries patent office and go from there.
I have been told by several people that this actually works. Reason is, that the post office has a stamp along with dates and is a legal government authority which would hold up in court as long as the mail has not been tampered with. The cheapest way to show you had the idea.
I would look into this for sure.