especially with "how to" videos all over youtube.

i do like the your idea with the metal pieces. smart and easy.

but still,
no better protection than the one that is on your hip.

Much easier and cheaper fix is a simple zip tie.

Solving the Breaking into a Garage problem - YouTube

The problem with zip tie is that it is hard to break it when you need to pull down the release handle...notice the amount of force needed in the video. Remember, if there is no play when you tighten the zip tie, it is NOT that easy to break.

In addition, in all likelihood, your car will be right under the garage opener when the power goes out. So, you will be reaching for the cord to pull down the handle at an angle while standing on your ladder (if your garage is high, like mine) reaching over...unless you like to step on your car's hood and roof and pull it from there!

In addition with my garage opener, you have to loop the zip tie all the way around the whole contraption and then under the release handle. And then you have to tighten it securely because you don't want the zip tie to slide off when the garage goes up and down repeatedly...and with it very tight, you go back to the initial problem of having to provide a lot of force to break the zip tie!

Which does no good if you're not home.

We have a wooden garage door and it's impossible to do that trick (I spent 10 minutes trying) but like was stated before if they want in your house then a window is an easy way in.
The best protection is good lock and more important it's good to have neighbors that pay attention or at least nosey ones.