Saw one of these key holder padlocks that you secure to your car in Bunning's for $17.90 I've seen them in the surf shops around the $60 mark. I had a play with it and it seemed quite robust so I bought one. Plenty more left in Bunnings.
Looks the same as the one I have, Bunnings for all you surf/sail/kite accessories 
May pay to keep it well lubed with some form of silicon spray or similar...
Mate has one, and it seized on him - ended up having to do the ol' under the fender trick... (Still - I guess with the keybox hanging there potential theives would just move on to the next car).
I just got a key cut with no electronic (just to open the doors) and wear it on a string around my neck, I hide the keys inside the car. Cost $ 5-00
^^^^^^ now that IS clever 'cat 
- more money left over for GROG , you're the winner
Yeah saw them at my bunnings today, but no price on thrm, so walked by. Though i already have one of the surfshop ones. Which i use religiously. Great idea.
Ir
a while ago I got a spare cut, whilst locking the real keys inside the car, the locksmith suggested that if you inadvertantly use the spare key to try and start the car, the computer says no and goes into meltdown, is it true? so now I just use the keysafe, I dont trust and old memory
i hide my key under the chassis. leave the doors open . there welcome to take all the McDonalds wrappers they can carry.
i just keep the key in the pocket in my boardies.....sorry forgot to add my boardies cost 70 skins
Don't put all your faith in this lock.
I was playing with one at Bunnings, almost brought it. Thought wonder if this is easy to crack like the old school one's we use to use for our pushies.
Had it open in less than 2mins.
I have been tempted to make a crude keysafe using a piece of pipe...
Using an appropriately sized piece of pipe, squash it 'flat' enough to be able to fit your car key inside it.
In one end drill (through both sides of the pipe) a hole large enough for a heavy duty padlock to go through, blank off the other end so the key cannot fall out (can be done by bashing flat, welding etc).
To use, just put your car key inside and padlock to your towbar etc. the padlock through the drilled hole stops the key from sliding out and keeps the whole lot attached to the car.
Keep the key for the padlock with you (tied to harness etc).
Hope this makes sense....
Mobile key guard car alarm is what you need, (technical name dog )
My staff bully stays in the van,( mercedes sprinter, auto aircon)
Try and get my keys out of the ignition where I usually leave them,
And you'll soon think a padlock is too easy !
All for the cost of an occasional scratch, and a couple of cookies,
(well, maybe a few pies tossed in for good measure)
Some of those car theives can actually pick a lock,
Yeah I know.......... amazes me too
