This new multiplayer game platform for the Apple iPhone from Neutron Games sounds promising, although no actual games are yet announced:
• Real-time, turn-based and tournament multiplayer options
• Game lobbies and various matchmaking capabilities
• Buddy lists, leaderboards, profiles, etc.
• In-game voice and text chat
• Billing and in-game microtransactions
I suppose I could do without the last part, but then again I buy stuff on Xbox Live and iTunes, so who am I to balk?