Smartlock Bike Lock -
SmartLock is a cable lock that has cores of compressed air and liquid running through its body. If cut, the liquids spray out over the perpetrator, his tools, the bike and the scene of the crime. A bike that has been stolen will be covered in coloured dye (the dye renders the bike undesirable and therefore unsellable) as well as translucent Smartwater - an invisible forensic property marking liquid.
Read all about it at: http://www.mikelambourn.com/smartlock.html