Love the old fashioned bit!
I actually recall the days of pre steering locks and Krooklock - hooking the clutch pedal to the steering wheel to prevent the clutch pedal being depressed.
I ran Morris 1000s for many years, after their production run time, and my favourite contribution to security was to fit a hidden switch in line with the electric fuel pump. This ensured the car could be found within a few hundred yards of where you parked it - having effectively run out of fuel! I frequently forgot to switch it back on, only to find the car almost coming to a standstill until I remembered to switch it back on.
Not beyond the bounds of some thought to fit something similar and covert to today's vehicles?
Kind regards,
Gareth.