[mdibiase]

For ease of use, you could also hide a fuel pump switch inside the car that you have to press before going. It's an easy but effective solution for protecting your car and needs basic tools / wires.

Of course, the important thing is making sure the wiring is well done (proper wire gauge) and the switch is actually in a hidden spot.

[olyjohn]

Magnetic switch hidden under your cup holders. And a magic cup with the right magnet glued to the bottom.

[blackboxlogic]

I installed a reed switch just under my windshield to unlock the doors. Swiping a magnet is easier than keeping a key in my pocket. Getting myself locked out is more of a concern than a stranger noticing the switch and finding a magnet. I'll even mention it on the internet, if any of you want to steal my car, please just fill up the gas and return it after. Thanks.