I have a very easy solution for this problem. it requires that the driver's side door be openable using a physical key to access to hood latch, and a switch capable of coping with the amperage flowing from the battery.
Open door, pop hood latch.
open hood latch, power up car from battery switch.
close hood, get it, key in, start up, drive off.
park the car, turn engine off, pop hood latch.
lock and close doors,
turn car off via battery switch, close hood, walk away.
Only way it can be stolen is via a flatbed rollback, or getting the hood popped open and manually kicking the battery back on. (no easy task on some cars!)