No SDK
VIXN does not require an SDK – it may be integrated server-side, but hey, if you want an SDK, we’ve got it.
VIXN, pronounced “vixen”, is the world’s first virtual item (VI) exchange network for mobile games. It allows inactive users to exchange their leftover VIs in one game for new VIs in another, using the VIXN ExchangeWall.

VIXN is a free cross-promotion service (if both games have the same owner), and optionally, a monetization solution (if they have different owners).
Who said adtech can’t be sexy anymore?