» How about garage door openers?

Yes, this technology will work for garage door openers. Garage door openers are typically controlled by a very few transmission codes and therefore if you drive around your neighborhood enough, hitting your garage door transmitter you will open a garage.

Once the controller/receiver is installed, and since each one can learn up to 30 switches, you can now get a secure door, from many locations - multiple cars, the garage, and the house.