Financial Institutions do this all the time whereby they have bundles of cash that contain dye packs. When a robbery is in progress, a bundle of cash with the dye pack is given to the robber which at a later time will explode, staining the thief with ink.

The Smart Lock by Michael Lambourn works on the same principle. The entire length of the lock is filled with a colored liquid. When a thief cuts the lock in an effort to steal the bike, the liquid explodes, covering both the ground and the thief with the colored liquid. By covering the ground and the thief, it is easier for police to place the thief at the scene of the crime. This in turn, makes it easier to lay charges.

[Michael Lambourn via Yanko Design]