SmartLock spatters bicycle thieves with paint
If there's one thing that Charlie Sorrel's tenure at Wired's Gadget Lab has ushered in, it is a daily infusion of posts in which Charlie complains about having his bicycle stolen by rampaging Barcelona junkie mutants, then asks his readers what a fair price is to buy his bicycle back from the same. If you met Charlie, you'd understand: an adult human with the muscular density of a cube of congealed milk scooped directly out of the past-expiry carton, he's effetely British besides, and incapable of the fortitude of will necessary to demand his bicycle back from known thieves or even call the police. As such, Gadget Lab's comment section — once the Algonquin Round Table of erudite gadget blog commenting — has essentially devolved into a community dedicated to discussing Charlie's probably genetic endowment of milksop wussiness.
Never the less, I like Charlie, and have been considering what to give him for Christmas. A scalp lacerating noogie, certainly, and perhaps a series of Indian burns and purple nurples, but I also thought maybe something to help him not get his bike stolen for once. So I considered for a moment this Smartock designed by Mike Lambourn, which sprays bike thieves who bolt-cut the locks with paint pellets. It's a good idea, co-opted from the paint explosives they pack into courier bags of bank currency. But Charlie already knows who is stealing his bikes, and most of them are recreational paint huffers besides. This will do him no good. What Charlie needs is a lock that will spray him with testosterone every time it is cut. And, you know, I just don't think that technology exists.

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I don't know.
Do I really want a pissed off, paint-covered criminal with bolt cutters waiting for me when I come to collect my bike?
I would prefer the lock-system shown in this link:
http://www.vk-international.com/engels/dubbelslot_engels.htm
It forces thieves to make multiple cuts in order to steal the bike.
My solution:
Get a bike that isn't worth stealing.
My bike looks like a rusty, dirty, $200-when-new piece of ordinary crap.
What your ordinary paint huffer doesn't notice, however, is that the cranks are aluminium, it's got top-end Shimano gears, elite saddle and that the 'rust' is sprayed on the aluminium/carbonfibre frame.
To top it off, I lock it with a $20 combination lock that any determined thief could break in 10 minutes flat.
The whole setup screams "crap", but the ride is sweeeeeet.
Can I replace the paint with cyanide?
A fine mist will almost immediately evaporate, and the corpse of the bike thief is bio degradable so that makes it's very environmentally friendly.
I think it might be worth losing a bike versus confronting a meth'd out thief. I've had bikes stolen (and even a scooter!) and while it pissed me off to no end, and even resulted in one ridiculous "high-speed" chase between a 3/4 ton pickup and a full size van, I would happily trade property for the lack of bullet hole scars (or worse).
Seriously, I tried to chase someone down while I was driving a 3/4 ton pickup. With a huge steel loading ramp in the back. It doesn't work well.
I shall call it "The Electro-Protector." A lock which carries a bank of extremely high voltage capacitors. When the pressure of bolt cutters is felt along it's outer surface, the inner, highly conductive surface becomes charged. The charge then travels along the bolt cutters, into the soon-to-be charred and mangled digits of a bike thief's crispy-fried corpse.
Even better...
I shall call it "The DHL Box Full of Scorpions." It's a DHL Box Full of Scorpions. When you steal the bike, they drop on you.
How about getting something that you cant cut through with bolt cutters? Like this:
http://www.kryptonitelock.com/Products/ProductDetail.aspx?cid=1001&scid=1002&pid=1168
I don't think the police are going to help you at all if you start going on about 'smart water'.
The test thief in the video didn't look too deterred, nor was he covered head to toe in bright yellow paint.
I prefer the South African version of this where the little paint balls are filled with Napalm.
I think it would work better with http://www.skunkshot.com/. Even meth heads don't want to smell that bad.
How about being smart about locking your bike with traditional locks? I use the Sheldon Brown method:
http://www.sheldonbrown.com/lock-strategy.html
Two locks of different types makes it more complicated to steal