The problem right now is persistent connections on iOS. You need to use push messages instead, which requires a plugin on the jabber server and a matching client.
Not something you can expect all your friends to set up.
Not something you can expect all your friends to set up.
MongooseIM doesn't support it either, although there is talk of it being implemented [1]
To be fair though, it was only accepted on the 18th March 2015.
[0] - https://www.ejabberd.im/protocols [1] - https://github.com/esl/MongooseIM/issues/405
FWIW, somebody is working on an ejabberd module [1], and there's some discussion [2] on the <standards@xmpp.org> mailing list.
(And ejabberd's community edition supports the XEPs that are relevant to mobile clients too, BTW.)
[1] - https://github.com/royneary/mod_push [2] - http://mail.jabber.org/pipermail/standards/2015-March/thread...