AdDuplex is running a contest where they will let developers win the most desirable objects still to be released.
They are offering a chance to win a Nokia Lumia 1520 or Surface 2 to developers who launch a Windows Phone or a Windows Store app on the AdDuplex network from the 12th September 2013 until the end of October.
Developers will be automatically entered, and the winner will be randomly selected and announced in early November, 2013, provided that the prizes are officially released by the time this campaign ends. The contest is open worldwide.
Head to the sweepstakes page for the details and official rules.