Ten bucks on the Wii Crystal Chronicles game.
Also, I got $50 on the Wii Animal Crossing.
Beyond that, Don't know.
Probably upcoming games that have both a DS version and a Wii version will have cross-link bonus content.
Like Metroid Prime and Metroid:Zero Mission, where linking them unlocked extra-hard (zero suit) mode on MP and Original Metroid on Zero Mission.