Tapping into a network can be tricky, but Skyzone wants to reach people who will pay for great games on their phone, so they sent out a free mini-game that people could play then forward to a friend with a challenge to play. The free game could lead to a game sale, but just collecting the phone number of potential players was the big win.

1to1 Magazine: Peer-to-Peer Marketing: Skyzone Dials Up Referral Results, 2006-Jul/Aug, by John Gaffney

Skyzone had two goals with Ragnorak. The first was to reach out to younger users through a mobile game that had offline components. The second was to convince wireless providers to license the game, which can be customized and forwarded to other users with its refer-to-a-friend feature.