The traditional U-lock is easy to cut. All it takes is seconds for thieves to saw through and haul your precious Koga Spyker Aeroblade away in their pickup. Daniel Idzkowski and Yves Perrenoud co-founded SkunkLock, a special type of lock that, when cut, emits a noxious spray in the thief's face. In 99% of tested subjects, the spray induced vomiting.
Currently, they are crowdfunding the invention and contributors of $99 or more will receive a lock in June 2017.
Source:
https://www.theguardian.com/lifeandstyle/2016/oct/21/bike-lock-developed-that-makes-thieves-immediately-vomit
https://www.indiegogo.com/projects/skunklock-the-only-bike-lock-that-fights-back-bicycle#/