Similar systems have been built into some commercial vehicles security
systems.  Don�t know exactly how they are implemented but have seen some
operating.  They worked with proximity switching.  A box on the operators
belt must be within a certain distance of the vehicle.  Too far away and
vehicle/equipment shuts down.  There was remote start and shutdown on the
box as well as an ignition style switch.
Personally I think a remote like this transmitting to a solenoid valve on
the input side of the fuel pump would be a nice touch.  Within range and
engine gets fuel, step off too far and the fuel pump gets no fuel.  Or
possibly same idea but to a control relay supplying power to the fuel pump.

  Don�t know what the control box and receiver would run but it could be
created with remote control airplane/toy car technology.  Then add a heavy
control relay about 20 bucks or a fuel solenoid for about 80 bucks to
control the fuel system.
jimt

On 8/15/05 5:07 AM, "Andrew Grebneff" <andrew.grebneff@STONEBOW.OTAGO.AC.NZ>
wrote:

>> 
>> How about if the thief drives out onto a big street, engine stops, brakes
>> activate, doors lock, windows close, and ... the gas canisters open.