I was searching and came across this amazing jira request for push server capability. This is exactly what I felt too, except didn't delve or earlier understand how to achieve this. http://jira.freeswitch.org/browse/FS-4347 This guy has identified very much what is really needed to be able to use it on smartphones. And suggests that Freeswitch and Csipsimple together show this capability where an incoming call or voicemail to a user using Csipsimple is notified through push notification. That starts Csipsimple (which is otherwise turned off) on his phone. This is a huge huge and amazingly useful thing since no one keeps their voip client on their phones on due to power consumption and battery drain ! This I think is the future of VOIP since smartphones are going to become soon huge % of voip clients.