Jabber for iPhone (version 8.6) and Jabber for IM (version 1.0.1).
I use WebEx (SaaS) for IM/P and so I don’t need VPN for my Jabber IM iPhone client.
For Jabber (Phone Client) I do have to VPN (Cisco Mobile Anyconnect app) to the existing ASA5520 (with Essentials and Mobile Connect licenses) to get to my UC cluster.
I have been using my Jabber for iPhone client, nonstop for the last 3 days across 600 miles driving toggling between Wifi and 3G with VPN traveling the speed limits, in and out of elevators, garages, etc. With the car charger plugged in and on battery. With iPhone idle in standby as well. It never disconnected.
I did set the Jabber to allow 3G VPN and I did notice some jitter and packet drop when crossing cell phone towers.
My office extension as CLID and the calls billed to my employer, added benefits.
Video calling on the Jabber Mobile iPhone client does require a wifi connection.
Using WebEx instant meeting (WebEx is not ‘native’ to the Jabber mobile client) is pretty seamless.
I can instantly escalate to a video call from Jabber IM chat session by clicking one button. Here is the target of my chat:

SO I am chatting and want to video with him. You see the contact card upper right? CLick that.

There is the button to click.

The WebEx Instant meeting started on its own, put me in it with Audio and ability to switch my camera (front and back) (in this scenario the Morkie is on the iPhone)

It Chatted the URL to the other person. I tried both federated AOL AIM and Google Gtalk clients and they both worked and they had no Jabber and no WebEx of their own.

The way it looked for the gmail user whn they clicked the URL follows: (yes, they needed a PW cause I set one.
And this would work integrated VoIP or with the PSTN Bridge I am using, where it also called them back.

Back to my view, I can still chat and switch cameras:

I DON’T NEED TO BE VPN CONNECTED TO MAKE THIS WORK. Jabber IM and WebEx don’t require it in SaaS operation.