Some sort of remote disabling device that you can use. Disable the car after you park it.
Maybe something simple like this disconnect:
https://www.summitracing.com/parts/sum-g1442
Maybe install it somewhere in the rear of the car either in the wheel well where it can't be seen or behind the rear bumper or body panel.
Only way to steal the car then is wench it onto a trailer or flatbed.