I have been researching along these lines lately as well, trying to be more 'real-time' I think for me is going to end up being some combination of xmpp(ejabberd) for the pushing and amqp(rabbitmq) for the brokering, proxying, queuing whatever you wanna call it google it and find some intersting projects along these lines already under way for a while
dbus-send --type=method_call --dest=com.nokia.modest /com/nokia/modest com.nokia.modest.SendReceive