A man from Raven Software has promised to pay for your copy of Wolfenstein if the game outsells Madden NFL 10 in August.
Manveer Heir said as much on his Twitter the other day, and later clarified that he would be using NPD numbers to confirm, and that if you keep your receipt and follow him on Twitter you're eligible, even if you live outside the US.
Heir, who is lead designer on an unannounced Raven game and describes himself as "an obsessive drunkard" on his profile, also added that this is only good for one copy per person.
"I know it's not likely that we beat Madden, but we gotta try!"
Madden NFL 10 is due out tomorrow, 14th August in Europe, while Wolfenstein should be available next Friday, 21st August. We'll certainly have a review of the latter soon, although next week's gamescom might hold it up.