Flutterby™! : Bike Mine

Going back through Google's spam filter (which is way too freakin' aggressive), another from Shadow: Bike Mine presents an explosive solution to bike theft:

The Bike Mine is a very simple mechanical alarm that uses a titanium trip wire, spring-action punch and shotgun blank commonly referred to as a "saluting blank," all housed in a rubber-wrapped steel body and attached to the bicycle via Velcro straps. The titanium wire gets connected to the wheel or nearby structure, so that when a bike thief moves the bike, the saluting blank goes off, creating a 150 dB blast to wake up the bicycle owner (and half the neighborhood) and ideally scare the thief off immediately.

Here's the (sadly canceled) Bike Mine kickstarter campaign