Fischer,
The mail-to-yourself trick would prove that you own the copyright over a work. A youtube video would work as well, since you automatically have copyright as soon as you create the work, you just need to prove you did it first.
However that does not grant you an automatic patent. That's a whole different process, that is much more complex. Virtually nobody files for a patent without going through a specialized lawyer.
Let me try to explain this to the best of my knowledge. Keep in mind that IANAL and this advice does not replace going to an actual lawyer if you want to pursue this further.
Say you compose a piece of music. You want to create something from your composition. It could be an mp3 recording, a Youtube video or a piece of paper sheet with the notes written on it. Your immediately have copyright over your creation. This means that you are free to dictate who's allowed to copy it, and under which conditions. (There are limits to copyright protection, but let's not get into this). However, let's say that I compose a similar piece of music. If I manage to prove that I did not
copy it, and my composition resembles yours out of pure coincidence (for instance, I was living in a cave in Basque country for 3 years and composed it while I was there), then you cannot prevent me from using my song as well as I please.
A patent is different. It doesn't cover a whole product. The iPhone is not patented, but it contains dozens of patented technologies. Say for instance, a gross simplification, you create a mechanism that produces much more combustion energy by mixing fuel with olive oil. You can then
apply for a patent. This is a much more complicated process. You have to produce a patent application that does, among other things:
- Describe exactly the technology you invented.
- Prove that no existing technology does what you claim to invent.
- Produce a big ass document filled with legalese mumbo jumbo.
If, and only if, your application gets accepted, then you'll be awarded the patent. At this point, you are granted monopoly for applications of this invention in every product in the market (for a theoretically short yet unfortunately too long period of time). At this point, any product that will use a olive oil combustion engine will owe you royalties. Even if they happened to invent at the same time as you did, or even before.
Patent law is extremely complicated. (So is copyright, for that matter). Don't trust me, I'm a random dude on the internet. Ask a lawyer, seriously.