Reference Article
stackoverflow: Multi-player server for iPhone application, using device as socket server.
stackoverflow: COMET (server push to client) on iPhone
Free (with iPhone API / SDK)
RedDwarf Server (Yes)
Stomp (Yes)
WebChat 2.0 (No)
Commercial (with iPhone API / SDK)
StreamHub (No, Web App)
SmartFoxServer Pro (Yes)
Exit Games Photon (Yes)