I\'m doing research for making a chat based app for the iPhone (it\'s not really text chat in the regular sense, but the principles are the same).
Maximum 6 people
XMPP sounds good for you idea, i think this is the best technology for Chat. It alos works great in iOS apps.
Maybe this code sample will be helpful to start using XMPP in iOS app - look at this QuickBlox Chat code sample. It demonstrates how to integrate 1-1 Chat, Chat in room into your android application. Also there is guide how it works. I think there will be no problem to integrate it into your application. Otherwise - Comments system below allows to ask any question you want and get fast answer.
Also there is Demo video http://www.youtube.com/watch?feature=player_embedded&v=SncQaJBBW_0 how this Chat works.