Lets look at the situation. Lean burning is a killer to an engine. If you have a race engine not getting enough gas it will blow the engine in short order. I would be surprised if cars such as NASCAR vehicles don't automatically cut the ignition on a loss of fuel pressure. At a drag strip you are very likely to blow your engine if not getting enough gas while doing that 1/4mile run at WOT. Losing your ignition doesn't harm your engine as far as I know. If you do cut the gas you HAVE to also cut the ignition as well to protect the engine. At WOT you CAN easily blow the engine cutting the fuel pump without cutting the ignition since you are slowly bleeding off the pressure and running for a few more cycles. If you cut the injectors it may be different since no fuel is being injected. And most waste spark systems will spark on an empty cylinder..
And as otherwise stated cutting power while running down the road is dangerous and will leave the maker of the device liable for damages caused by accidents caused by shutting down the engine while moving. The Proper way to do this is to cut the ignition when the car has come to a complete stop. I would probably also make sure the brake pedal is applied to ensure the car is not rolling still.
As to secure connections.. You could have your vehicle check in every so often and if it doesn't get a signal to shut its self down and to prevent any starting etc. So hiding it wouldn't accomplish much.
My security system will have multiple backup batteries as will my CarPC... Plus they will talk to each other making any attempts to steal the vehicle very annoying to the thief.