You could run the real XMPP client on a server and use the native push messaging system to wake up the mobile client. This would also enable receiving "offline" messages while the mobile device is not on a network or turned off.

Of course, this would let the person operating the "real" XMPP client read your messages; but the person operating the XMPP server can do that already, so there isn't any real change -- either way you should be using OTR messaging at all times.

In the peer to peer spirit of XMPP, such a project should make it really easy to run this virtual client yourself locally or on a cheap cloud server. Maybe something like that exists already? Anybody wanna build it?