Need to somehow make the entire car live when there's nobody in it, that'll give them the fright of their lives!! Problem is the HR police wouldn't have it as some scrote with a heart condition will come along and claim they were only looking at your car or brushing past it. Suppose we can't have innocent people getting zapped left right and centre.
Maybe a Knightrider affair whereby the car works out if the individual is a trouble maker or not, and takes appropriate action.
Or, cars should come with 360 degree discreet CCTV as a security option and big warning stickers all over the place.