Another extension that draw my attention is BOSH which uses XMPP over HTTP solving the issue of unreliable connections and also Firewalled TCP ports
BOSH certainly allows XMPP where only a unblocked HTTP(S) connection is available. But it does not automatically solve the issue of unreliable connections.
This is not due BOSH itself but because the BOSH code lacks a developer who takes care of it. All I did was to fork jbosh over to ignite realtime and include the patches from aSmack to make jbosh Android compatible (basically replacing the HTTP client library and fixing a regex). But since I personally don't use the code I only take care that everything compiles and looks ok. That's why smack-bosh's description reads "This API is considered beta quality".
jbosh itself has some issues (e.g. the unit tests a non-deterministic), and requires some attention.
I've reports that it works more or less, but that there are delays up to a few minutes (just search the forum). This is most likely related to how polling is implemented. But since I don't use BOSH, it's not on my todo list to look into this.
I hope that one day some skilled developer appears, willing to take care of BOSH, providing some good unit, stress and integration tests.