The campaign involves Nestle chocolate bars KitKat 4 Finger, KitKat Chunky, Aero Peppermint and Yorkie Milk.
Three thousand six-sheet posters have been fitted with NFC and QR touchpoints that will direct smartphones to a mobile landing page.
The landing page offers the chance to enter a secondary competition with an on-pack code via Facebook, and informs people how many of the original six GPS-fitted bars are left. There are six prizes to be won.
Outdoor specialist Posterscope has placed ads created by JWT on posters owned by Clear Channel, Primesight and JCDecaux, on behalf of media agency Mindshare.
Posterscope claims that out-of-home is fast becoming a "recognised physical portal" through which consumers can connect instantly with the online content of their favourite brands.
In July, Nestlé appointed JWT London to handle its UK digital marketing account for the Kit Kat brand.Follow @nickbatten2