Hi guys,
This might have some use for you in cold mornings when often doing engine ON and OFF's, or just for security when buying a newspaper in local shop and leaving car running outside. It is called RunLock relay, really handy divice.
Simply arm the RunLock, take the key with you, it can be disarmed only when key is back in ignition barrel. If the handbrake lever will be released witout key being in - the engine will cut off.
http://premierhazard.co.uk/products/78-rl001-runlock
and simple wiring
http://premierhazard.co.uk/resources/files/32705b049f6753bd0de397c7ba364410/D00176-1-A%20RUNLOCK%20FITTING%20INSTRUCTIONS.pdf
There is one on fleebay from a differnt manufacturer, the Premier Hazard one isn't low quality unit as it's approved and in use by UK police forces when arriving at scene.
Regards