To participate, all you need is a computer, Android, or iPhone and a heaping helping of chutzpah. Start by visiting ds4seekers.citroen.co.uk and signing up for the game. Every day, Citroën will give you a new virtual DS4, which you can customize and "hide" anywhere you like using Google Street View (via Citroën's Facebook page) or Citroën's DS4Seekers app. Hiding a DS4 will give you 5 points.
Then, use Street View or the smartphone app to locate DS4s that other players have hidden. Each virtual DS4 you collect will give you additional points. (Using the app instead of the Facebook page earns bonus points, too.) At the end of the competition, each point will count as a sweepstakes entry in a drawing for a new DS4.
Of course, there are some rules and regs -- namely, you have to be a U.K. resident with a valid driver's license. And if you haven't already begun playing, you'll need to get on the ball -- the contest ends tomorrow, July 28, at 5pm GMT. Good luck!
P.S. This video won't offer much additional info, but it's an easy way to kill a few spare seconds on a Wednesday: