Smart Lock, the Exploding Bike Lock
The Smart Lock by Michael Lambourn is filled with pressurized, colored liquid and explodes upon being cut. Along the lines of the exploding ink used in banks, it is startling and makes the culprit that much more identifiable. Not on the market yet and likely not the most practical of lock designs, it is pretty interesting nonetheless. Click through for a video of the design in action, staining everything in sight once compromised with bolt cutters.